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Sample records for corotation resonance rossby

  1. Three-Dimensional Alignment and Corotation of Weak, TC-like Vortices via Linear Vortex Rossby Waves.

    NASA Astrophysics Data System (ADS)

    Reasor, Paul D.; Montgomery, Michael T.

    2001-08-01

    The vertical alignment of an initially tilted geostrophic vortex is shown here to be captured by linear vortex Rossby wave dynamics when the vortex cores at upper and lower levels overlap. The vortex beta Rossby number, defined as the ratio of nonlinear advection in the potential vorticity equation to linear radial advection, is less than unity in this case. A useful means of characterizing a tilted vortex flow in this parameter regime is through a wave-mean flow decomposition. From this perspective the alignment mechanism is elucidated using a quasigeostrophic model in both its complete and linear equivalent barotropic forms. Attention is focused on basic-state vortices with continuous and monotonically decreasing potential vorticity profiles.For internal Rossby deformation radii larger than the horizontal scale of the tilted vortex an azimuthal wavenumber 1 quasi mode exists. The quasi mode is characterized by its steady cyclonic propagation, long lifetime, and resistance to differential rotation, behaving much like a discrete vortex Rossby wave. The quasi mode traps disturbance energy causing the vortex to precess, or corotate, and thus prevents alignment. For internal deformation radii smaller than the horizontal vortex scale, the quasi mode disappears into the continuous spectrum of vortex Rossby waves. Alignment then proceeds through the irreversible redistribution of potential vorticity by the sheared vortex Rossby waves. Further decreases in the internal deformation radius result in a decreased dependence of vortex evolution on initial tilt magnitude, consistent with a reduction of the vortex beta Rossby number.These results are believed to have relevance to the problem of tropical cyclone (TC) genesis. Cyclogenesis initiated through the merger and alignment of low-level convectively generated positive potential vorticity within a weak incipient vortex is captured by quasi-linear dynamics. A potential dynamical barrier to TC development in which the quasi

  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. 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

  4. 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

  5. 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.

  6. 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

  7. A theory of stationary long waves. I - A simple theory of blocking. II - Resonant Rossby waves in the presence of realistic vertical shears

    NASA Technical Reports Server (NTRS)

    Tung, K. K.; Lindzen, R. S.

    1979-01-01

    A theory of stationary long waves in the atmosphere is developed, with attention given to the blocking phenomenon caused by the resonant amplification of large-scale planetary waves in a uniform zonal flow and to resonant Rossby waves in an atmosphere with winds varying with height. A simple model is presented to illustrate the temporal behavior of Rossby waves forced by topography and differential heating of the land and the sea, using a beta-plane approximation and assuming a spatially uniform zonal wind which may vary in time, and quasi-geostrophic disturbances. Results are then extended to the case of resonant Rossby waves in the presence of realistic vertical shears. Numerical experiments in which the wind profiles are varied in a number of physically possible manners reveal the most favorable wind configurations for resonance.

  8. 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.

  9. Derivation of capture probabilities for the corotation eccentric mean motion resonances

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

    We study in this paper the capture of a massless particle into an isolated, first-order corotation eccentric resonance (CER), in the framework of the planar, eccentric and restricted three-body problem near a m + 1: m mean motion commensurability (m integer). While capture into Lindblad eccentric resonances (where the perturber's orbit is circular) has been investigated years ago, capture into CER (where the perturber's orbit is elliptic) has not yet been investigated in detail. Here, we derive the generic equations of motion near a CER in the general case where both the perturber and the test particle migrate. We derive the probability of capture in that context, and we examine more closely two particular cases: (i) if only the perturber is migrating, capture is possible only if the migration is outward from the primary. Notably, the probability of capture is independent of the way the perturber migrates outward; (ii) if only the test particle is migrating, then capture is possible only if the algebraic value of its migration rate is a decreasing function of orbital radius. In this case, the probability of capture is proportional to the radial gradient of migration. These results differ from the capture into Lindblad eccentric resonance (LER), where it is necessary that the orbits of the perturber and the test particle converge for capture to be possible.

  10. 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.

  11. Corot Telescope: COROTEL

    NASA Astrophysics Data System (ADS)

    Viard, Thierry; Bodin, Pierre; Magnan, A.; Baglin, A.

    2007-09-01

    The space Corot telescope has been developed by Thales Alenia Space Cannes (previously named Alcatel Alenia Space) and has been delivered to the French Space agency (CNES. The satelllite has veen successfully launched from BaÃkonour the 27th of December 2006. This telescope is a very precise and stable imaging instrument that is pointed towards fixed areas in the sky for periods of at least 5 month, in order to carry out two kinds of missions: (i) Stellar seismology, (ii) Search for exoplanets (by transit detection). Corot is likely to be the first space instrument capable of detecting Earth like planets orbiting around other stars and providing accurate stellar data in relation with their internal constitution. The target stars will have visible magnitudes lower than 9 for the seismology mission, and lower than 13 for the detection of Earth-like planets. COROT is a low cost mission and has a polar circular orbit with an altitude around 800 Km (unfortunately not at L2 orbit). In order to comply with the above objectives, the instrument shall deliver a very stable signal from a stable source. More particularly, this stringent stability requirement implies: (i) a high level of straylight (coming from earth) rejection, (ii) a high pointing stability, (iii) a high level of performance for the thermal control subsystem in term of temperature and gradient stability associated with the use of hyper stable materials. On the other hand, this instrument is carried by a low size satellite associated with the use of hyper stable materials. On the other hand, this instrument is carried by a low size satellite of the PROTEUS family, allowing a faster and cheaper development. This paper focuses on the proposed opto mechanical design for the telescope, its baffling cancept and its performance which are now demonstrated in flight.

  12. Corotation torques in the solar nebula - The cutoff function

    NASA Technical Reports Server (NTRS)

    Ward, William R.

    1989-01-01

    The behavior of high-order corotation resonances in a disk of finite thickness is examined. The torque exerted at an mth-order resonance is determined by employing a vertically averaged disturbing function, and the ratio of this torque to that exerted on a cold, two-dimensional disk is identified as the so-called torque cutoff function. This function is then used to calculate contributions from the corotation torques to eccentricity variations of a perturber's orbit assumed orbiting in the disk.

  13. The Caribbean Rossby Whistle: Mesoscale Influence on Coastal Sea Level.

    NASA Astrophysics Data System (ADS)

    Williams, J.; Hughes, C. W.; Hibbert, A.; Boening, C.; Oram, J. P.

    2016-12-01

    We show that there is a resonant baroclinic Rossby basin mode in the Caribbean Sea, with a period of 120 days. The mode is excited by mesoscale instability of the Caribbean Current, so is analogous in operation to a whistle. It consists of a wavenumber 2 Rossby wave propagating to the west across the basin. The wave interacts with topographically-steered currents along the continental slope, meaning that as it fades on the west of the basin, it is reborn on the east. This interaction with boundary currents leads to the mode being a major source of coastal sea level variability. Because the basin is not closed, it also produces a basinwide bottom pressure signal which dominates bottom pressure variability in the region.

  14. Nonlinear Dynamics of Magnetohydrodynamic Rossby Waves and the Cyclic Nature of Solar Magnetic Activity

    NASA Astrophysics Data System (ADS)

    Raphaldini, Breno; Raupp, Carlos F. M.

    2015-01-01

    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.

  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. 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.

  17. Rossby wave extra invariant in the Galerkin approximation

    NASA Astrophysics Data System (ADS)

    Balk, Alexander M.

    2017-08-01

    The non-linear system of Rossby waves or plasma drift waves is known to have a unique adiabatic-like extra invariant in addition to the energy and enstrophy. This invariant is physically significant because its presence implies the generation of zonal flow. The latter is known to slow down the anomalous transport of temperature and particles in nuclear fusion with magnetic confinement. However, the derivation of the extra invariant - unlike the energy and enstrophy - is based on the continuum of resonances, while in numerical simulations there are only finite number of resonances. We show that precisely the same invariant takes place in the Galerkin approximations (even of low order, with a few ODEs). To show this we make variation of boundary conditions, when the solution is periodic in different directions. We also simplify the derivation of the extra conservation.

  18. 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.

  19. Coupling Coefficients In The Kinetic Theory of Rossby Waves

    NASA Astrophysics Data System (ADS)

    Soomere, T.

    Rossby waves serve as an example of wave systems where resonant energy exchange between different wave classes with comparable frequencies can occur. Energy ex- change in such systems can be described with a system of equations called multi- wave (multi-modal) kinetic equation. Multi-wave kinetic equations typically contain two sets of coefficients describing energy exchange intensity. Interaction coefficients describe interaction intensity within a particular set of resonant waves. The coupling coefficients limit energy exchange within specific types of interactions. The interaction coefficients solely depend on the dispersion relations of the interacting wave compo- nents whereas the coupling coefficients represent the structure of the non-linear parts of the wave equations. One of the simplest multi-wave kinetic equations describes slow evolution of the energy spectrum of baroclinic Rossby waves in a multi-layer model ocean. Explicit expressions for the coupling coefficients in the case of a N-layer ocean are obtained and their main properties are established. A part of the expressions is fairly general. It is demonstrated that several types of interactions vanish in the case of simple realistic vertical structures of the ocean. For example, it is well know that in the two-layer case the intensity of energetic changes within resonant sets containing solely baroclinic harmonics crucially depends on the ratio of the depths of the layers. In the case of equal depths, self-interactions of the baroclinic mode fully cease, be- cause the corresponding coupling coefficient vanishes. This property suggests that an improper choice of the model may result in a completely different evolution scenario of the whole system. The detailed analytic expressions for the coupling coefficients of the Rossby wave kinetic equation are derived for a three-layer model ocean. If the re- duced depths of the uppermost and the lowermost layers are equal, a number of differ- ent interaction

  20. 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.

  1. Revisiting the Corotation Electric Field

    NASA Astrophysics Data System (ADS)

    Rothwell, P. L.

    2001-05-01

    The rotation of the Earth's dipole magnetic field produces a corotation electric field in the nonrotating frame of reference. A quick calculation implies that this field might arise from the relative motion of an observer in the nonrotating frame and the motion of rotating magnetic field lines. However, upon applying Faraday's Law one finds that total time rate of change of the magnetic field as seen in the nonrotating frame is zero due to the azimuthal symmetry of the dipole. Therefore, classical EM theory(1) predicts a zero corotation electric field in the nonrotating frame for a vacuum. This conundrum has been traditionally treated in the following manner(2,3). 1) Start with a vacuum state with no conductors and plasma present. The transformation between E (the electric field in the nonrotating frame) and E' (the electric field in the rotating frame)implies that in the rotating frame E' is nonzero while E = 0. 2) In the presence of a thin conducting spherical shell (the ionosphere) polarization charges form in the shell due to the magnetic force on the electrons. A polarization electric field Ep is created such that in the idealized case the shell has a uniform electric potential. This Ep has a component along the magnetic field lines outside the shell. 3) Plasma will polarize along B, thus canceling the parallel component of Ep which allows the potential on the shell to be mapped along the magnetic field lines setting E' = 0. From the transformation equation E is now nonzero. This is the electric field required in the nonrotating frame for the plasma to corotate with the dipole. The presence of the corotation electric field is not a local result, but a nonlocal effect that requires the presence of an ionosphere and a conducting plasma. (1) W.K.H. Panofsky and M. Phillips, Classical Electricity and Magnetism, Addison-Wesley, 1956. (2) H. Alfven and C.-G. Falthammar, Cosmical Electrodynamics, 2nd ed., Oxford Press, 1963. (3) E.W.Hones and J.E.Bergeson, J. Geophys

  2. The Peculiar Behavior of the Large-Scale Components of the Solar Magnetic Field as a Result of Rossby Vortex Excitation beneath the Convection Zone

    NASA Astrophysics Data System (ADS)

    Tikhomolov, E. M.; Mordvinov, V. I.

    1996-11-01

    To interpret the dynamical features of large-scale magnetic fields, Rossby vortices are considered. Rossby vortices are assumed to be excited and sustained within a thin layer beneath the convection zone as a result of heating from the solar interior and deformation of the covection zone lower boundary. Numerical calculations show that a Rossby cyclone generates a large-scale magnetic structure, whose horizontal size compares with the solar radius. The distribution of the vertical component of the magnetic field bears a resemblance in this case to the cloud distribution in the cyclones that are observed in the Earth's atmosphere. A magnetic field with the sign of trailing polarity flux of the local bipolar magnetic regions and a field with the sign of leading polarity are generated, respectively, at the center of the Rossby cyclone and at the periphery. The drift of the cyclone toward the Sun's pole, caused by the Rossby wave emission, leads to a corresponding drift of the large-scale magnetic structure. Longitudinally averaged magnetic field distribution also drifts poleward and has a form of "double surge." The leading polarity is the first to reach the pole. The rotation of the first Fourier components of magnetic field calculated for the low- and midlatitude belts resembles in this case the real picture during the threefold polar field reversal in solar activity cycle. Rossby cyclones are used also to simulate some other situations on the Sun when, according to observational data, there are weak drifts of the longitudinally averaged component and corotation of the first Fourier components of the low- and midlatitude belts.

  3. Corot, une mission bien remplie

    NASA Astrophysics Data System (ADS)

    Baglin, Annie; Belkacem, Kevin; Chaintreuil, Sylviane; Deleuil, Magali; Lam-Trong, Thien

    2017-03-01

    The CoRoT mission developped since 1993 was dedicated to the observation of ultra high precision measurements of the variations of stellar fluxed on long and continuous durations. His two major objectives were the detection of stellar oscillations and of extrasolar planets. A a pionnier mission, it had to invent several methods and to built the successive steps of the data treatment. They are rapidly described. The low cost 'CNES Petites Missions" programme imposed severe contraints on the instrument concept (Organisation and management, choice of the detectors, of the orbit, reduction of all parasite lights) which have been and will be guides for new generation projects. Some scientific highlights are then presented on both programmes, as for instance the use of the seismic tool as an indicator of the structure and evolution of the Galaxy, the first detection of a super-Earth, and the first precise characterisation of a brown dwarf . CoRoT has opened several avenues in instrumentation as well as science. It is shown how some aspects of this heritage have been used in the design and development of its two major heiress: CHEOPS to be launched in 2018 and the more ambitious PLATO, to be launched in 2025.

  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. COROT: asteroseismology and planet finding

    NASA Astrophysics Data System (ADS)

    Baglin, A.; Auvergne, M.; Barge, P.; Buey, J.-T.; Catala, C.; Michel, E.; Weiss, W.; COROT Team

    2002-01-01

    The COROT project, developed in the framework of the CNES small satellite program with a wide European cooperation, will be launched in 2004. It is dedicated to seismology and detection of telluric planets. It will perform relative broad band photometry in visible light, during very long (150 days) observing runs in the same direction. Both programs are working simultaneously on the same region of the sky. The seismology program aims at mapping the H-R diagram and study in details approximately 50 targets brighter than 9th magnitude. Another 50 will also be observed with a lower accuracy. The exoplanet program will search for telluric planets slightly larger than the Earth, in the habitable zone and closer.

  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. MHD Simulations: Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Wiengarten, T.; Kleimann, J.; Fichtner, H.; Kissmann, R.

    2014-09-01

    Corotating Interaction Regions (CIRs) form in the solar wind when parcels of fast-speed wind interact with slow-speed wind due to the rotation of the Sun. The resulting buildup of pressure generates disturbances that, with increasing time (or distance from the Sun), may develop into a so-called forward-reverse shock pair. During solar-quiet times CIRs can be the dominant force shaping large-scale structures in the heliosphere. Studying CIRs is therefore important because the associated shocks are capable of e.g. accelerating energetic particles or deflecting cosmic rays. The global structure of CIRs can be modeled with an MHD approach that gives the plasma quantities needed to model the transport of particles in the heliosphere with e.g. stochastic differential equations. Here, we show results from 3D-MHD simulations with our code CRONOS for a) analytic boundary conditions where results can be compared to those obtained with a different code and b) boundary conditions derived with the Wang-Sheeley-Arge model from observational data (WSO), which are compared to spacecraft observations.

  8. Rossby wave, drift wave and zonal flow turbulence

    NASA Astrophysics Data System (ADS)

    Quinn, Brenda E.

    An extensive qualitative and quantitative study of Rossby wave, drift wave and zonal flow turbulence in the Charney-Hasegawa-Mima model is presented. This includes details of two generation mechanisms of the zonal flows, evidence of the nonlocal nature of this turbulence and of the energy exchange between the small and large scales. The modulational instability study shows that for strong primary waves the most unstable modes are perpendicular to the primary wave, which corresponds to the generation of a zonal flow if the primary wave is purely meridional. For weak waves, the maximum growth occurs for off-zonal modulations that are close to being in three-wave resonance with the primary wave. Nonlinear jet pinching is observed for all nonlinearity levels but the subsequent dynamics differ between strong and weak primary waves. The jets of the former further roll up into Karman-like vortex streets and saturate, while for the latter, the growth of the unstable mode reverses and the system oscillates between a dominant jet and a dominant primary wave. A critical level of nonlinearity is defined which separates the two regimes. Some of these characteristics are captured by truncated models. Numerical proof of the extra invariant in Rossby and drift wave turbulence is presented. 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 Fjortoft 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 wellknown 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

  9. Normal mode Rossby waves observed in the upper stratosphere

    NASA Technical Reports Server (NTRS)

    Hirooka, T.; Hirota, I.

    1985-01-01

    In recent years, observational evidence has been obtained for westward traveling planetary waves in the middle atmosphere with the aid of global data from satellites. There is no doubt that the fair portion of the observed traveling waves can be understood as the manifestation of the normal mode Rossby waves which are theoretically derived from the tidal theory. Some observational aspects of the structure and behavior of the normal model Rossby waves in the upper stratosphere are reported. The data used are the global stratospheric geopotential thickness and height analyses which are derived mainly from the Stratospheric Sounding Units (SSUs) on board TIROS-N and NOAA satellites. A clear example of the influence of the normal mode Rossby wave on the mean flow is reported. The mechanism considered is interference between the normal mode Rossby wave and the quasi-stationary wave.

  10. Rossby waves with linear topography in barotropic fluids

    NASA Astrophysics Data System (ADS)

    Yang, Liangui; da, Chaojiu; Song, Jian; Zhang, Huiqin; Yang, Hongli; Hou, Yijun

    2008-08-01

    Rossby waves are the most important waves in the atmosphere and ocean, and are parts of a large-scale system in fluid. The theory and observation show that, they satisfy quasi-geostrophic and quasi-static equilibrium approximations. In this paper, solitary Rossby waves induced by linear topography in barotropic fluids with a shear flow are studied. In order to simplify the problem, the topography is taken as a linear function of latitude variable y, then employing a weakly nonlinear method and a perturbation method, a KdV (Korteweg-de Vries) equation describing evolution of the amplitude of solitary Rossby waves induced by linear topography is derived. The results show that the variation of linear topography can induce the solitary Rossby waves in barotropic fluids with a shear flow, and extend the classical geophysical theory of fluid dynamics.

  11. MHD simulations: Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Wiengarten, T.; Kleimann, J.; Fichtner, H.; Kühl, P.; Heber, B.; Kissmann, R.

    2013-12-01

    Corotating Interaction Regions (CIRs) form in the solar wind when parcels of fast-speed wind interact with slow-speed wind due to the rotation of the Sun. The resulting buildup of pressure generates disturbances that, with increasing time (or distance from the Sun), may develop into a so-called forward-reverse shock-pair. During solar-quiet times CIRs can be the dominant force shaping large-scale structures in the heliosphere. Studying CIRs is therefore important because the associated shocks are capable of e.g. accelerating energetic particles or deflecting cosmic rays. The global structure of CIRs can be modeled with an MHD approach that gives the plasma quantities needed to model the transport of particles in the heliosphere (with e.g. stochastic differential equations (SDEs)). Our MHD code CRONOS employs a semi-discrete finite volume scheme with adaptive time-stepping Runge-Kutta integration. The solenoidality of the magnetic field is ensured via constrained transport and the code supports Cartesian, Cylindrical and Spherical coordinates (including coordinate singularities) with the option for non-equidistant grids. The code runs in parallel (MPI) and supports the HDF5 output data format. Here, we show results from 3D-MHD simulations with our code CRONOS for a) analytic boundary conditions where results can be compared to those obtained with a different code and b) boundary conditions derived with the Wang-Sheeley-Arge model from observational data (WSO), which are compared to spacecraft observations. Comparison with Pizzo (1982) for analytic boundary conditions Comparison with STEREO A for Carrington Rotation 2060

  12. Baroclinic Rossby Wave Signature in a General Circulation Ocean Model.

    DTIC Science & Technology

    1983-06-01

    northwest with a wavelength cf 300 km. For other laritudes of the North acific Ocean , Price and Maqaard (1980) determined that first mode baroclinic Rossby...role in the latitude belt 40-50N in the North acific 10 -. - !o Ocean . Magaard (1983) ir. a paper discussing bariclin _c Rossty wave energetics...HD-AI132 219 BAROCLINIC ROSSBY WAVE SIGNATURE IN A GENERAL CIRCULATION OCEAN MODEL(U) NAVAL POSTGRADUATE SCHOOLU MONTEREY CA A H RUTSCH JUN 83

  13. Arctic Ocean Centennial-Scale Rossby modes

    NASA Astrophysics Data System (ADS)

    Petersen, M.; Hjorth, P.; Schmith, T.

    2009-04-01

    The Arctic Ocean has a characteristic stable stratification with fresh and cold water occupying the upper few hundred meters and with warm and more saline Atlantic waters underneath. These water masses are separated by the cold halocline. The stability of the cold halocline regulates the upward directed turbulent heat flux from the Atlantic water to the Arctic water. Since this heat flux is an important part of the ocean energy budget it is important for the large scale sea ice formation and melting. Due to the sable vertical stratification combined with its almost circular symmetry the Arctic Ocean may support internal Rossby modes. In this study we investigate these modes in a theoretical framework. We apply the free surface two layer model with a linear damping on the sphere and solve this in idealised geometries. We solve this system numerically by a finite difference scheme based on the Arakawa C-grid. We find that solutions to the system have a damping time scale comparable to the propagation time scale, both in the order of a few centuries. Furthermore, this damping time scale is rather independent of the local damping coefficient. For a circular symmetric geometry the amplitude is zero at the boundary. Interestingly, for a more realistic sector-geometry we find finite amplitudes at the borders. We interpret this in the model as anomalies in the halocline height being exported as fresh water anomalies via the Fram Strait where they further south they may modulate deep water formation and strength of the thermohaline circulation.

  14. Topographic Rossby Waves Generated by Tropical Cyclones

    NASA Astrophysics Data System (ADS)

    Dukhovskoy, D. S.; Morey, S. L.

    2013-05-01

    Analytical and numerical studies suggest that given appropriate slope, the ocean responds to a tropical storm with low-frequency motions trapped over a continental slope, the Coastal Trapped Waves. The presented study is focused on Topographic Rossby Waves (TRW), sub-inertial oscillations propagating over a sloping bottom. Generation and propagation of TRW under barotropic (Continental Shelf Waves or Shelf Waves) and baroclinic (Bottom Trapped Waves) approximations are discussed. A real-case model study of a storm surge in Apalachee Bay, northeastern Gulf of Mexico during Hurricane Dennis (July, 2005) is presented to demonstrate the role of the shelf waves in coastal inundation. The presentation also discusses excitation of baroclinic bottom-intensified wave motions on the continental slope by a tropical cyclone. An idealized model experiment demonstrates that a continental shelf that (1) responds to a storm as a baroclinic ocean and (2) has a slope steep enough to dominate the planetary β-effect (but small enough to prevent internal Kelvin-type modes) can support baroclinic topographic waves.

  15. 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.

  16. Europe looks forward to COROT launch

    NASA Astrophysics Data System (ADS)

    2006-12-01

    While CNES is completing preparations for the launch from Baikonur/Kazakhstan, ESA and a large number of European scientists involved in the mission are eagerly awaiting this event and the first scientific results to come through. What is COROT? COROT stands for ‘Convection Rotation and planetary Transits’. The name describes the mission’s scientific goals. ‘Convection and rotation’ refer to the satellite’s capability to probe stellar interiors, studying the acoustic waves that ripple across the surface of stars, a technique called asteroseismology. ‘Transit’ refers to the technique whereby the presence of a planet orbiting a star can be inferred from the dimming starlight caused when the planet passes in front of it. To achieve its twin scientific objectives, COROT will monitor some 120,000 stars with its 30-centimetre telescope. COROT will lead a bold new search for planets around other stars. In the decade since the first discovery in 1995 of an exoplanet (51 Pegasi b), more than 200 other such planets outside our solar system have been detected using ground-based observatories. The COROT space telescope promises to find many more during its two-and-a-half-year mission, expanding the frontiers of our knowledge towards ever-smaller planets. Many of the planets COROT will detect are expected to be 'hot Jupiters', gaseous worlds. An unknown percentage of those detected are expected to be rocky planets, maybe just a few times larger than the Earth (or smaller, even). If COROT finds such planets, they will constitute a new class of planet altogether. While it is looking at a star, COROT will also be able to detect 'starquakes', acoustic waves generated deep inside a star that send ripples across its surface, altering its brightness. The exact nature of the ripples allows astronomers to calculate the star's precise mass, age and chemical composition. COROT’s European dimension The COROT mission was first proposed by CNES back in 1996. A call for

  17. Understanding Rossby wave trains forced by the Indian Ocean Dipole

    NASA Astrophysics Data System (ADS)

    McIntosh, Peter C.; Hendon, Harry H.

    2017-06-01

    Convective variations over the tropical Indian Ocean associated with ENSO and the Indian Ocean Dipole force a Rossby wave train that appears to emanate poleward and eastward to the south of Australia and which causes climate variations across southern Australia and more generally throughout the Southern Hemisphere extratropics. However, during austral winter, the subtropical jet that extends from the eastern Indian Ocean into the western Pacific at Australian latitudes should effectively prohibit continuous propagation of a stationary Rossby wave from the tropics into the extratropics because the meridional gradient of mean absolute vorticity goes to zero on its poleward flank. The observed wave train indeed exhibits strong convergence of wave activity flux upon encountering this region of vanishing vorticity gradient and with some indication of reflection back into the tropics, indicating the continuous propagation of the stationary Rossby wave train from low to high latitudes is inhibited across the south of Australia. However, another Rossby wave train appears to emanate upstream of Australia on the poleward side of the subtropical jet and propagates eastward along the waveguide of the eddy-driven (sub-polar) jet into the Pacific sector of the Southern Ocean. This combination of evanescent wave train from the tropics and eastward propagating wave train emanating from higher latitudes upstream of Australia gives the appearance of a continuous Rossby wave train propagating from the tropical Indian Ocean into higher southern latitudes. The extratropical Rossby wave source on the poleward side of the subtropical jet stems from induced changes in transient eddy activity in the main storm track of the Southern Hemisphere. During austral spring, when the subtropical jet weakens, the Rossby wave train emanating from Indian Ocean convection is explained more traditionally by direct dispersion from divergence forcing at low latitudes.

  18. 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.

  19. 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.

  20. 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.

  1. Influence of mid-ocean ridges on Rossby waves

    NASA Technical Reports Server (NTRS)

    Wang, Liping; Koblinsky, C. J.

    1994-01-01

    Influence of mid-ocean ridges on Rossby wave activity is discussed in simple models. Ridges can influence Rossby waves in two ways, topographic scattering to model parameters such as frequency, ridge height, and ridge width in both barotropic and baroclinic models. In the barotropic model, for certain model parameters there is perfect transmission of Rossby waves, while for some other model parameters the transmission is rather weak. In a two-layer model, if the frequency is not low enough, trapping of baroclinic signals around topography will occur. The mid-ocean ridge is generally not as efficient as the eastern boundary in generating barotropic waves except at high frequencies in a barotropic model. It is much more efficient than the eastern boundary generating baroclinic waves when wind forcing has a very large zonal scale, while less efficient when wind forcing has a short zonal scale.

  2. On the meridional structure of extra-tropical Rossby waves

    NASA Astrophysics Data System (ADS)

    Ashkenazy, Yosef; Paldor, Nathan; Zarmi, Yair

    2011-08-01

    The common derivation of Rossby waves is based on the quasi-geostrophic approximation. A simple non-harmonic approximation for extratropical Rossby waves on the sphere is proposed, in which the meridional coordinate is a parameter instead of a continuous variable. It is shown that, in contrast to the quasi-geostrophic solution, to first order the meridional structure of these non-harmonic Rossby waves becomes irrelevant for determining the dispersion relation in this theory. The proposed approximation accurately reproduces numerical results obtained from runs of an ocean general circulation model initiated from several initial meridional structures and captures the latitudinal dependence of the phase speed of these waves. The proposed theory yields explicit expressions for the dispersion relation and for the meridional structure of the waves.

  3. 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

  4. Inertial Instability and Rossby Wave Breaking in a Numerical Model.

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Donal J.; Hitchman, Matthew H.

    1992-06-01

    A mechanistic model of the middle atmosphere is used to study the interaction between Rossby waves forced at the extratropical tropopause and inertial instability in the equatorial lower mesosphere. The impact of cross-equatorial shear strength and Rossby wave forcing amplitude is explored. Model results support the hypothesis, based on satellite temperature observations, that Rossby waves organize regions of equatorial inertial instability into coherent large-scale circulations. Horizontal convergence and divergence maxima are found stacked over the boundaries of regions of anomalous potential vorticity (PV). This supports observational diagnoses and theoretical expectations that parcel inertial accelerations arise in regions of anomalous PV, with divergence and convergence occurring at the boundaries. Although cross-equatorial shear determines the initial volume of inertially unstable air, Rossby waves arriving from the winter hemisphere deform PV contours such that zonally confined regions of anomalous PV extend well into the winter hemisphere and somewhat into the summer hemisphere. Significant parcel inertial accelerations are diagnosed to occur in anomalous PV tongues to 30° latitude in the winter hemisphere. Using a smaller cross-equatorial shear delays the penetration of anomalous PV into the winter hemisphere, while increasing the Rossby wave forcing amplitude causes a more rapid evolution of the low-latitude flow.These results suggest that inertial instability is intimately involved in Rossby wave breaking in the subtropical winter mesosphere. The horizontal scales of inertially unstable regions coevolve with those of PV anomalies, and so affect the breaking process from inception. The vertical scale of inertial circulations is much smaller than that of Rossby waves; hence, Rossby wave PV anomalies are eroded by vertical mixing as well as horizontal mixing. Gravity waves radiate away from the inertially unstable regions, which effectively convert energy

  5. Equatorial Rossby Waves and Periodicities of Flare Activities

    NASA Astrophysics Data System (ADS)

    Lou, Y.-Q.

    2000-05-01

    The Gamma-Ray Spectrometer (GRS) aboard the Solar Maximum Mission (SMM) first revealed a 154-day periodicity in solar flare rates. Subsequently, periodicities in various solar flare activities and sunspot areas or groups during a few years around solar maxima have been extensively monitored using different diagnostics and at many electromagnetic wavelengths. Notable periods are ~ 154, 128, 102, 78 and 51 days during maxima of different solar cycles from various data sets. The origin of such long-time periodicities particularly prominent during solar maxima remains a mystery for nearly two decades. For slow and large-scale photospheric dynamics, the shallow magnetofluid approximation can be invoked when the Rossby number R0≡ U/(2Ω sun L) is small, where U (< ~ 103 cm s-1) and L (≳ Rsun) are typical horizontal velocity and spatial scales. Physical properties of equatorially trapped Kelvin waves, Poincaré waves, Rossby waves and mixed Rossby-Poincaré waves are examined. For typical solar parameters, period estimates of Rossby and mixed Rossby-Poincaré waves are ~ 151-155, 126-127, 101-102, 76-78 and 51-54 days in good agreement with inferred periodicities. The effect of large-scale subsurface magnetic fields is estimated. Two methods (i.e., surface velocity correlations and precise diameter measurements) of directly detecting equatorially trapped solar Rossby-type waves are emphasized. Plausible connections among the large-scale photospheric wave dynamics, Rossby radius of deformation, sunspot zones, subsurface magnetic fields, magnetic flux emergence, active regions and solar flare activities are discussed. The scenario of a dynamic feedback cycle is advanced for excitations of these low-frequency Rossby-type waves during solar maxima. It would be of considerable interest to examine whether large-scale coronal mass ejections also carry the similar periodicities in the current solar maximum using SOHO observations. This work was supported in part by grants of

  6. 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.

  7. 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.

  8. Poleward Moisture Transport Associated with Subtropical Rossby Wave Breaking

    NASA Astrophysics Data System (ADS)

    Kiladis, G. N.; Albers, J.; Dias, J.; Newman, M.

    2015-12-01

    Rossby wave activity propagating into low latitudes and associated wave-breaking events frequently lead to the onset of convection within the deep tropics through dynamical processes that are still incompletely understood. The orientation of these wave-breaking events also results in poleward transport of moisture from the tropics and subtropics on synoptic time scales. The time mean manifestation of this transport in the Southern Hemisphere results in "diagonal convergence zones" such as the South Pacific Convergence Zone (SPCZ) and South Atlantic Convergence Zone (SACZ). In the Northern Hemisphere, such geographically anchored convergence zones are much less evident, which presumably reflects a less zonally asymmetry in the distribution of the location of extratropical wave activity interacting with low latitudes. The relationship between extratropical Rossby wave activity, Rossby wave breaking events and poleward moisture transport is quantified on synoptic through interannual time scales in this study. While there are certainly preferred paths for moisture transport within both hemispheres, the lack of diagonal convergence zones within the Northern Hemisphere is shown to be a result of larger intraseasonal variability in the path of Rossby wave propagation. Nevertheless, the preferred path of this wave activity does lead to a local precipitation maximum in the eastern North Pacific ITCZ during northern winter.

  9. 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.

  10. 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.

  11. Large amplitude stationary Rossby waves in the Southern Hemisphere

    NASA Technical Reports Server (NTRS)

    Kalnay, E.; Halem, M.

    1981-01-01

    Large Amplitude stationary waves downstream of South America, and in the lee of Australia were investigated using Tiros N photographs. These waves appear to be Rossby lee waves associated with anomalous poleward flow over the Andes and by continental heating over Australia. The waves have a maximum amplitude near 300 mb between 20 and 40 deg S and correlate well with observed precipitation bands in the Atlantic and Pacific Oceans. The orientation of these waves is such that they transfer zonal momentum to the roaring forties latitudes. Stationary Rossby waves, in the Northern Hemisphere, have a characteristic wavelength of the order of 120 deg longitude. In January the observed stationary wavelengths have a wavelength of less than 60 deg longitude with an amplitude in the upper tropospheric meridional wind of more than 15 m sec E-1.

  12. An experimental investigation of the Rossby two-slit problem

    NASA Astrophysics Data System (ADS)

    Kaminski, Alexis; Pedlosky, Joseph; Helfrich, Karl

    2016-11-01

    Rossby waves, which arise in response to buoyancy or winds at the sea surface, are a common feature of the oceans, and the problem of Rossby wave propagation in closed basins is a classical problem in geophysical fluid dynamics. Theoretical models of ocean circulation in basins with incomplete barriers such as ocean ridges or island chains (e.g.) suggest that barriers extending through most of a basin are surprisingly inefficient at blocking the transmission of Rossby wave energy from one subbasin to the next. However, the existing theory neglects nonlinear effects and friction in the main basin interiors. To examine these effects, here we present the results of a series of experiments performed over a range of forcing frequencies and amplitudes, in which particle image velocimetry is used to measure the flow field. We find that while the linear theory appears to capture the large-scale structures of the flow, viscosity and nonlinearity significantly affect the flow along the boundaries and near the gaps in the barrier. This project was funded by a 2014 WHOI GFD Fellowship.

  13. The detection of Rossby-like waves on the Sun

    NASA Astrophysics Data System (ADS)

    McIntosh, Scott W.; Cramer, William J.; Pichardo Marcano, Manuel; Leamon, Robert J.

    2017-03-01

    Rossby waves are a type of global-scale wave that develops in planetary atmospheres, driven by the planet's rotation1. They propagate westward owing to the Coriolis force, and their characterization enables more precise forecasting of weather on Earth2,3. Despite the massive reservoir of rotational energy available in the Sun's interior and decades of observational investigation, their solar analogue defies unambiguous identification4-6. Here we analyse a combined set of images obtained by the Solar TErrestrial RElations Observatory (STEREO) and the Solar Dynamics Observatory (SDO) spacecraft between 2011 and 2013 in order to follow the evolution of small bright features, called brightpoints, which are tracers of rotationally driven large-scale convection7. We report the detection of persistent, global-scale bands of magnetized activity on the Sun that slowly meander westward in longitude and display Rossby-wave-like behaviour. These magnetized Rossby waves allow us to make direct connections between decadal-scale solar activity and that on much shorter timescales. Monitoring the properties of these waves, and the wavenumber of the disturbances that they generate, has the potential to yield a considerable improvement in forecast capability for solar activity and related space weather phenomena.

  14. 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.

  15. Exoplanet discoveries with the CoRoT space observatory

    NASA Astrophysics Data System (ADS)

    Lammer, H.; Dvorak, R.; Deleuil, M.; Barge, P.; Deeg, H. J.; Moutou, C.; Erikson, A.; Csizmadia, Sz.; Tingley, B.; Bruntt, H.; Havel, M.; Aigrain, S.; Almenara, J. M.; Alonso, R.; Auvergne, M.; Baglin, A.; Barbieri, M.; Benz, W.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Cabrera, J.; Carone, L.; Carpano, S.; Ciardi, D.; Ferraz-Mello, S.; Fridlund, M.; Gandolfi, D.; Gazzano, J.-C.; Gillon, M.; Gondoin, P.; Guenther, E.; Guillot, T.; den Hartog, R.; Hasiba, J.; Hatzes, A.; Hidas, M.; Hébrard, G.; Jorda, L.; Kabath, P.; Léger, A.; Lister, T.; Llebaria, A.; Lovis, C.; Mayor, M.; Mazeh, T.; Mura, A.; Ollivier, M.; Ottacher, H.; Pätzold, M.; Pepe, F.; Pont, F.; Queloz, D.; Rabus, M.; Rauer, H.; Rouan, D.; Samuel, B.; Schneider, J.; Shporer, A.; Stecklum, B.; Steller, M.; Street, R.; Udry, S.; Weingrill, J.; Wuchterl, G.

    2010-12-01

    The CoRoT space observatory is a project which is led by the French space agency CNES and leading space research institutes in Austria, Brazil, Belgium, Germany and Spain and also the European Space Agency ESA. CoRoT observed since its launch in December 27, 2006 about 100 000 stars for the exoplanet channel, during 150 days uninterrupted high-precision photometry. Since the The CoRoT-team has several exoplanet candidates which are currently analyzed under its study, we report here the discoveries of nine exoplanets which were observed by CoRoT. Discovered exoplanets such as CoRoT-3b populate the brown dwarf desert and close the gap of measured physical properties between usual gas giants and very low mass stars. CoRoT discoveries extended the known range of planet masses down to about 4.8 Earth-masses (CoRoT-7b) and up to 21 Jupiter masses (CoRoT-3b), the radii to about 1.68 × 0.09 R Earth (CoRoT-7b) and up to the most inflated hot Jupiter with 1.49 × 0.09 R Earth found so far (CoRoT-1b), and the transiting exoplanet with the longest period of 95.274 days (CoRoT-9b). Giant exoplanets have been detected at low metallicity, rapidly rotating and active, spotted stars. Two CoRoT planets have host stars with the lowest content of heavy elements known to show a transit hinting towards a different planethost-star-metallicity relation then the one found by radial-velocity search programs. Finally the properties of the CoRoT-7b prove that rocky planets with a density close to Earth exist outside the Solar System. Finally the detection of the secondary transit of CoRoT-1b at a sensitivity level of 10-5 and the very clear detection of the "super-Earth" CoRoT-7b at 3.5 × 10-4 relative flux are promising evidence that the space observatory is being able to detect even smaller exoplanets with the size of the Earth.

  16. Evidence for Corotating Convection in Saturn's Magnetosphere

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

    Saturn's magnetic field exhibits a high degree of azimuthal symmetry, yet the field and plasma signatures of the magnetosphere are modulated at a period close to that of planetary rotation. How, then, is a clear periodicity imposed on the magnetic field and plasma of the planetary magnetosphere? In this talk, Cassini magnetometer data are used to develop a scenario for the dynamics of the Saturn magnetosphere. The proposal is that mass transport, accomplished in the inner magnetosphere by interchange motion, feeds into the outer magnetosphere where ballooning driven by centrifugal stress leads to outward transport, field reconnection and plasma loss in a favored local time sector; flux is transported inward in other regions. The model is closely related to the concept of corotating convection proposed by Dessler, Hill, and co-workers for Jupiter. The proposed mechanism can be consistent with aspects of the empirical camshaft model introduced by Espinosa et al., 2003 to explain Pioneer and Voyager magnetometer data. Anomalous transport here proposed could originate from a localized ionospheric conductivity anomaly. The resulting cyclic stress modulates the current in the current sheet and can account for its north-south excursions. The convection patterns proposed also imply that corotating, field-aligned currents would be a basic feature of the Saturn system.

  17. A note on free and forced Rossby wave solutions: The case of a straight coast and a channel

    NASA Astrophysics Data System (ADS)

    Graef, Federico

    2017-03-01

    The free Rossby wave (RW) solutions in an ocean with a straight coast when the offshore wavenumber of incident (l1) and reflected (l2) wave are equal or complex are discussed. If l1 = l2 the energy streams along the coast and a uniformly valid solution cannot be found; if l1,2 are complex it yields the sum of an exponentially decaying and growing (away from the coast) Rossby wave. The channel does not admit these solutions as free modes. If the wavenumber vectors of the RWs are perpendicular to the coast, the boundary condition of no normal flow is trivially satisfied and the value of the streamfunction does not need to vanish at the coast. A solution that satisfies Kelvin's theorem of time-independent circulation at the coast is proposed. The forced RW solutions when the ocean's forcing is a single Fourier component are studied. If the forcing is resonant, i.e. a free Rossby wave (RW), the linear response will depend critically on whether the wave carries energy perpendicular to the channel or not. In the first case, the amplitude of the response is linear in the direction normal to the channel, y, and in the second it has a parabolic profile in y. Examples of these solutions are shown for channels with parameters resembling the Mozambique Channel, the Tasman Sea, the Denmark Strait and the English Channel. The solutions for the single coast are unbounded, except when the forcing is a RW trapped against the coast. If the forcing is non-resonant, exponentially decaying or trapped RWs could be excited in the coast and both the exponentially ;decaying; and exponentially ;growing; RW could be excited in the channel.

  18. 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

  19. Corotating Magnetic Reconnection Site in Saturn’s Magnetosphere

    NASA Astrophysics Data System (ADS)

    Yao, Z. H.; Coates, A. J.; Ray, L. C.; Rae, I. J.; Grodent, D.; Jones, G. H.; Dougherty, M. K.; Owen, C. J.; Guo, R. L.; Dunn, W. R.; Radioti, A.; Pu, Z. Y.; Lewis, G. R.; Waite, J. H.; Gérard, J.-C.

    2017-09-01

    Using measurements from the Cassini spacecraft in Saturn’s magnetosphere, we propose a 3D physical picture of a corotating reconnection site, which can only be driven by an internally generated source. Our results demonstrate that the corotating magnetic reconnection can drive an expansion of the current sheet in Saturn’s magnetosphere and, consequently, can produce Fermi acceleration of electrons. This reconnection site lasted for longer than one of Saturn’s rotation period. The long-lasting and corotating natures of the magnetic reconnection site at Saturn suggest fundamentally different roles of magnetic reconnection in driving magnetospheric dynamics (e.g., the auroral precipitation) from the Earth. Our corotating reconnection picture could also potentially shed light on the fast rotating magnetized plasma environments in the solar system and beyond.

  20. Corotation Lag in Jupiter's Magnetosphere: Comparison of Observation and Theory.

    PubMed

    Hill, T W

    1980-01-18

    Voyager 1 plasma flow data are compared with a recent theory that predicted measurable departures from rigid corotation in Jupiter's magnetosphere as a consequence of rapid plasma production and weak atmosphere-magnetosphere coupling. The comparison indicates that the theory can account for the observed corotation lag, provided that the plasma mass production rate during the Voyager 1 encounter was rather larger than expected, namely approximately 10(30) atomic mass units per second.

  1. 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.

  2. Rossby waves on the Sun as revealed by solar 'hills'

    PubMed

    Kuhn; Armstrong; Bush; Scherrer

    2000-06-01

    It is a long-standing puzzle that the Sun's photosphere--its visible surface--rotates differentially, with the equatorial regions rotating faster than the poles. It has been suggested that waves analogous to terrestrial Rossby waves, and known as r-mode oscillations, could explain the Sun's differential rotation: Rossby waves are seen in the oceans as large-scale (hundreds of kilometres) variations of sea-surface height (5-cm-high waves), which propagate slowly either east or west (they could take tens of years to cross the Pacific Ocean). Calculations show that the solar r-mode oscillations have properties that should be strongly constrained by differential rotation. Here we report the detection of 100-m-high 'hills' in the photosphere, spaced uniformly over the Sun's surface with a spacing of (8.7 +/- 0.6) x 10(4) km. If convection under the photosphere is organized by the r-modes, the observed corrugated photosphere is a probable surface manifestation of these solar oscillations.

  3. Characteristics of Kelvin waves and Mixed Rossby-Gravity waves in opposite QBO phases

    NASA Astrophysics Data System (ADS)

    Zaman Fathullah, Nur; Lubis, Sandro W.; Setiawan, Sonni

    2017-01-01

    A 35-year ERA-Interim dataset from the European Center for Medium-Range Weather Forecasts (ECMWF) was used to study the characteristics of Kelvin waves and Mixed Rossby-gravity waves based on a Space-Time Spectral Analysis (STSA). The results show that Kelvin wave activity is stronger during easterly QBO phases, while Mixed Rossby-gravity waves are stronger during westerly QBO phases. Analysis on seasonal variations indicates that the Kelvin waves and Mixed Rossby-Gravity wave activities increase in JJA and SON, respectively. This is associated with a variation of basic mean flow in the lower stratosphere. In addition, the variations of Kelvin and Mixed Rossby-Gravity waves in the troposphere are not significantly affected by the QBO phases. In the troposphere, both Kelvin waves and Mixed Rossby-Gravity waves propagate with a lower phase speed compared to those observed in the stratosphere. This behavior is to be likely due to large.

  4. CoRoT in Brief

    NASA Astrophysics Data System (ADS)

    Boisnard, L.; Auvergne, M.

    2006-11-01

    The CoRoT Space Telescope is an experiment of astronomy dedicated to stellar seismology and search for extrasolar planets. The mission is led by CNES in association with French laboratories and with a significant international participation: ESA (Science Programme and RSSD/ESTEC, Austria, Belgium, Germany contribute to the payload, whereas Spain and Brazil (who has recently joined the project) contribute to the ground segment. Based on a PROTEUS low earth orbit recurrent platform, the spacecraft has been in development since October 2000 for a launch scheduled in Ocotber 2006. It gives an overview of the experiment, explains where the critical scientific requirements are for payload engineering and describes the cost-effective compromises found for high accuracy photometry in low earth orbit. We run through the different families of perturbations due to the interaction between the spacecraft and its environment and illustrate how some noise contributors, which generate spectral lines likely to be misinterpreted as a component of the star signal, are reduced by design, avoided by an appropriate mission profile or corrected after calibration. We focus on the following technical issues: telescope baffling and orbital drift, pointing stability, optoelectronics thermal regulation, light curve processing

  5. Rossby Wave Instability in the Accretion Flows around Black Holes

    NASA Astrophysics Data System (ADS)

    Gholipour, Mahmoud

    2017-01-01

    The roles of the Rossby wave instability (RWI) have been significantly developed in some important processes, such as planet formation and angular momentum transport through thin accretion disks. However, their development on accretion flows with advection is insignificant. In this paper, we investigate the effect of advection in the occurrence of RWI through accretion flows around black holes (BHs). In the absence of advection, the occurrence of RWI is extremely low because of high viscosity in the accretion flows around BHs. The results of this paper show that there is a significant chance for the occurrence of RWI in some wavelengths if we consider advection even in low amounts. Therefore, the RWI can be a suitable candidate for angular momentum transport in the accretion flows around BHs. Also, the results show that the advection parameter and the ratio of heat capacity, which are special characters of advection flows, play important roles in the occurrence of RWI.

  6. Rossby waves, extreme fronts, and wildfires in southeastern Australia

    NASA Astrophysics Data System (ADS)

    Reeder, Michael J.; Spengler, Thomas; Musgrave, Ruth

    2015-03-01

    The most catastrophic fires in recent history in southern Australia have been associated with extreme cold fronts. Here an extreme cold front is defined as one for which the maximum temperature at 2 m is at least 17°C lower on the day following the front. An anticyclone, which precedes the cold front, directs very dry northerlies or northwesterlies from the interior of the continent across the region. The passage of the cold front is followed by strong southerlies or southwesterlies. European Centre for Medium-Range Weather Forecasts ERA-Interim Reanalyses show that this regional synoptic pattern common to all strong cold fronts, and hence severe fire conditions, is a consequence of propagating Rossby waves, which grow to large amplitude and eventually irreversibly overturn. The process of overturning produces the low-level anticyclone and dry conditions over southern Australia, while simultaneously producing an upper level trough and often precipitation in northeastern Australia.

  7. Rossby numbers of fully convective and partially convective stars

    NASA Astrophysics Data System (ADS)

    Landin, Natália R.; Mendes, Luiz T. S.

    2017-10-01

    In this work, we investigate the stellar magnetic activity in the theoretical point of view, through the use of stellar structure and evolution models. We present theoretical values of convective turnover times and Rossby numbers for low-mass stars, calculated with the ATON stellar structure and evolution code. We concentrate our analysis on fully convective and partially convective stars motivated by recent observations of X-ray emission of slowly rotating fully convective stars, which suggest that the presence of a tachocline is not a central key for magnetic fields generation. We investigate the behavior of the convective turnover time evolution, as well as its radial profile inside the star. A discussion about the location where the convective turnover time is calculated in the stellar interior is also addressed. Our theoretical results are compared to observational data from low-mass stars.

  8. 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.

  9. CoRoT: Harvest of the exoplanet program

    NASA Astrophysics Data System (ADS)

    Moutou, Claire; Deleuil, Magali; Guillot, Tristan; Baglin, Annie; Bordé, Pascal; Bouchy, Francois; Cabrera, Juan; Csizmadia, Szilárd; Deeg, Hans J.

    2013-11-01

    One of the objectives of the CoRoT mission is the search for transiting extrasolar planets using high-precision photometry, and the accurate characterization of their fundamental parameters. The CoRoT satellite consecutively observes crowded stellar fields since February 2007, in high-cadence precise photometry; periodic eclipses are detected and analyzed in the stellar light curves. Then complementary observations using ground-based facilities allows establishing the nature of the transiting body and its mass. CoRoT has acquired more than 163,000 light curves and detected about 500 planet candidates. A fraction of them (5%) are confirmed planets whose masses are independently measured. Main highlights of the CoRoT discoveries are: (i) the variety of internal structures in close-in giant planets, (ii) the characterization of the first known transiting rocky planet, CoRoT-7b, and (iii) multiple constraints on the formation, evolution, role of tides in planetary systems.

  10. 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.

  11. Oceanic Rossby waves acting as a "hay rake" for ecosystem floating by-products.

    PubMed

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

    2003-11-28

    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.

  12. Synoptic-scale nonlinear stationary magnetized Rossby waves in the ionospheric E-layer

    SciTech Connect

    Kaladze, T. D.; Horton, W.

    2006-12-15

    Magnetized Rossby waves are produced by a dynamo electric field and represent the ionospheric generalization of tropospheric Rossby waves in a rotating atmosphere with a spatially inhomogeneous geomagnetic field. They are described by the modified Charney-Obukhov equation with a Poisson-bracket convective nonlinearity. This type of equation has solutions in the form of synoptic-scale nonlinear solitary dipole vortex structures of 1000-3000 km in diameter. With the use of equivalence conditions, various stationary nonlinear solutions are obtained and investigated analytically. The basic characteristics of stationary vortex structures for magnetized Rossby waves are investigate000.

  13. Geomagnetic Effects of Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Vršnak, Bojan; Dumbović, Mateja; Čalogović, Jaša; Verbanac, Giuliana; Poljanǐć-Beljan, Ivana

    2017-09-01

    We present an analysis of the geoeffectiveness of corotating interaction regions (CIRs), employing the data recorded from 25 January to 5 May 2005 and throughout 2008. These two intervals in the declining phase of Solar Cycle 23 are characterised by a particularly low number of interplanetary coronal mass ejections (ICMEs). We study in detail how four geomagnetic-activity parameters (the Dst, Ap, and AE indices, as well as the Dst time derivative, dDst/dt) are related to three CIR-related solar wind parameters (flow speed, V, magnetic field, B, and the convective electric field based on the southward Geocentric solar magnetospheric (GSM) magnetic field component, VBs) on a three-hour time resolution. In addition, we quantify statistical relationships between the mentioned geomagnetic indices. It is found that Dst is correlated best to V, with a correlation coefficient of cc≈0.6, whereas there is no correlation between dDst/dt and V. The Ap and AE indices attain peaks about half a day before the maximum of V, with correlation coefficients ranging from cc≈0.6 to cc≈0.7, depending on the sample used. The best correlations of Ap and AE are found with VBs with a delay of 3 h, being characterised by cc≳ 0.6. The Dst derivative dDst/dt is also correlated with VBs, but the correlation is significantly weaker cc≈ 0.4 - 0.5, with a delay of 0 - 3 h, depending on the employed sample. Such low values of correlation coefficients indicate that there are other significant effects that influence the relationship between the considered parameters. The correlation of all studied geomagnetic parameters with B are characterised by considerably lower correlation coefficients, ranging from cc=0.3 in the case of dDst/dt up to cc=0.56 in the case of Ap. It is also shown that peak values of geomagnetic indices depend on the duration of the CIR-related structures. The Dst is closely correlated with Ap and AE (cc=0.7), Dst being delayed for about 3 h. On the other hand, d

  14. 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

  15. Framing topographic Rossby waves in the Southern Adriatic Sea

    NASA Astrophysics Data System (ADS)

    Bonaldo, Davide; Orlic, Mirko; Bergamasco, Andrea; Benetazzo, Alvise; Carniel, Sandro

    2017-04-01

    Topographic Rossby Waves (TRWs) are oscillatory phenomena associated with modulations induced by seabed morphology in the potential vorticity field. These features could be confined to a single layer or could involve the whole water column, and they are controlled by a combination of the bathymetric gradient and the uniform rotation in the same way as planetary Rossby waves are controlled by the meridional modulation of the Coriolis parameter. In terms of deep-sea circulation, TRWs provide a fundamental contribution by radiating large amounts of energy along and off a continental shelf. Under favorable conditions TRWs can be triggered by a number of factors, such as intense vorticity injections from the wind or the bathymetric perturbations - e.g., a promontory or a canyon crossing the path of a current. In this work we combine observational data and numerical model fields for detecting the presence of TRWs along the Southern Adriatic Margin (SAM, Eastern Mediterranean Sea) and investigating their dynamics during an episode of dense water downflow in spring 2012. Starting from the observation of high-intensity velocity pulses with a period of approximately 2 days, we carry out a sequence of operations on the results of a high-resolution, ocean currents-waves coupled numerical modelling experiment aiming to reproduce dense water formation and migration in the Adriatic Sea in winter-spring 2012. First, we apply a wavelet analysis to modelled velocity time series at several locations off the Italian coast and along the SAM in order to identify the spatial and temporal extent of the pulsing episodes. Then, the properties of the oscillations are assessed via rotary analysis; the propagation of the band-filtered signal along the continental margin is characterized by extracting wave length and propagation velocity, therefore allowing the comparison against theoretical dispersion relations associated with the bathymetry of the SAM. Our results show that the observed

  16. A closure for eddy-mean flow effects based on the Rossby wave energy equation

    NASA Astrophysics Data System (ADS)

    Eden, Carsten; Olbers, Dirk

    2017-06-01

    The concept of IDEMIX was recently developed to simulate and parameterize the effect of gravity waves on the large-scale circulation. It is applied here to Rossby waves. Since gravity wave drag is formally identical to baroclinic instability it appears possible to parameterize the effect of baroclinic and barotropic instability on the large-scale circulation following the IDEMIX concept which is based here on the Rossby wave energy equation in physical and phase space. The dimensions of that equation are reduced by assuming a fixed shape of the energy spectrum with respect to horizontal wave number. The result is a set of coupled conservation equations for Rossby wave energy compartments resolved in horizontal direction and wave vector angle. Using simple parameterisations for wave-wave interaction, the performance of the closure is tested in an idealized model of baroclinic and barotropic instability where the Rossby waves are assumed to contain the subgrid-scale energy.

  17. Determining the Co-Rotation Radius of Nearby Spiral Galaxies Using Spiral Arm Overlays

    NASA Astrophysics Data System (ADS)

    Shameer Abdeen, Mohamed; Kennefick, Daniel; Kennefick, Julia D.; Pour Imani, Hamed; Shields, Douglas W.; Eufrasio, Rafael; Berlanga Medina, Jazmin; Monson, Erik

    2017-01-01

    Density wave theory, originally proposed by C.C. Lin and Frank Shu (Lin & Shu 1964), views the spiral arm structures in spiral galaxies as density waves that propagates through the galactic disk. Resonances within orbits create standing wave patterns of density waves that we observe as spiral arms. The theory predicts the existence of a radius known as the co-rotation radius in which the spiral arm pattern speed matches the velocities of the stars within the disk. We introduce a novel way of determining the co-rotation radius, based on an image overlaying technique, which involves tracing the arms of spiral galaxies on images observed from different wavelengths. For the purpose of this study, 12 nearby galaxies were analyzed from four different wavelengths using pitch angle measurements from a previous study (Hamed et al. 2016). We used optical wavelength images (B-Band,440 nm), two infrared wavelength (Infrared; 3.6 µm and 8 µm) Spitzer Space Telescope images and ultraviolet images from GALEX. The results were verified by checking against results compiled from the literature.

  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. On double Rossby wave breaking in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Messori, Gabriele; Caballero, Rodrigo

    2015-11-01

    We discuss the dynamical features associated with double Rossby wave breaking (DWB, concurrent cyclonic and anticyclonic breakings) over the North Atlantic, with a focus on the North Atlantic Oscillation (NAO), the midlatitude jet stream, and surface wind extremes over continental Europe. Objective automated algorithms for detecting wave breaking and determining the location, intensity, and direction of the jet are adopted. The analysis is performed on the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis and the Max Planck Institute Earth System Model (MPI-ESM). We find that DWB events can project onto both phases of the NAO, albeit showing no strong preference for either. Wave-breaking pairs occurring in the northern North Atlantic project onto the positive NAO, while the opposite holds for pairs occurring farther south. DWB also affects the direction and intensity of the jet stream. Events in the eastern half of the basin (EWB) intensify and zonalize the jet, while events farther to the west (WWB) weaken the westerly flow over Europe. An analysis of destructive wind storms over Europe in the last three decades suggests that these are typically associated with a very intense, zonal jet—similar to the case of EWB. Indeed, EWB corresponds to an enhanced likelihood of destructive windstorms over the continent, although there is not a one-to-one correspondence. The MPI-ESM model does not capture this statistical relationship. On the contrary, WWB corresponds to a decreased likelihood of destructive weather.

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

    PubMed

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

    2016-09-09

    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.

  1. 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.)

  2. Formation of plasmasphere in the non-ideal corotation field

    NASA Astrophysics Data System (ADS)

    Dumin, Yurii

    It is well-known that the standard model of plasmasphere formation by the combined action of convection and the ideal corotation fields is too simplified and does not describe some important features. One of attempts to improve it was undertaken a few years ago in our paper [1], where we considered generation of the corotation field in the strongly-anisotropic magnetospheric plasma and took into account distortion of this field in high latitudes due to escape of the polarization charges along the open magnetic field lines. In the present report, we further develop the idea of refinement of the corotation field, particularly, by the consideration of the magnetic dipole inclined with respect to the rotation axis. It will be shown that all the above-mentioned improvements result in the more adequate description of the position of plasmapause both in the quiet and disturbed conditions. References: 1. Yu.V. Dumin. The Corotation Field in Collisionless Magnetospheric Plasma and Its Influence on Average Electric Field in the Lower Atmosphere. Advances in Space Research, v.30, p.2209 (2002).

  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 COROT ground-based archive and access system

    NASA Astrophysics Data System (ADS)

    Solano, E.; González-Riestra, R.; Catala, C.; Baglin, A.

    2002-01-01

    A prototype of the COROT ground-based archive and access system is presented here. The system has been developed at LAEFF and it is based on the experience gained at Laboratorio de Astrofisica Espacial y Fisica Fundamental (LAEFF) with the INES (IUE Newly Extracted System) Archive.

  5. 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.)

  6. Stellar classification of CoRoT targets

    NASA Astrophysics Data System (ADS)

    Damiani, C.; Meunier, J.-C.; Moutou, C.; Deleuil, M.; Ysard, N.; Baudin, F.; Deeg, H.

    2016-11-01

    Context. The CoRoT mission was the first dedicated to the search for exoplanets from space. The CoRoT exoplanet channel observed about 163 600 targets to detect transiting planetary companions. In addition to the search for exoplanets, the extremely precise photometric time series provided by CoRoT for this vast number of stars is an invaluable resource for stellar studies. Because CoRoT targets are faint (11 ≤ r ≤ 16) and close to the galactic plane, only a small subsample has been observed spectroscopically. Consequently, the stellar classification of CoRoT targets required the design of a classification method suited for the needs and time frame of the mission. Aims: We describe the latest classification scheme used to derive the spectral type of CoRoT targets, which is based on broadband multi-colour photometry. We assess the accuracy of this spectral classification for the first time. Methods: We validated the method on simulated data. This allows the quantification of the effect of different sources of uncertainty on the spectral type. Using galaxy population synthesis models, we produced a synthetic catalogue that has the same properties as the CoRoT targets. In this way, we are able to predict typical errors depending on the estimated luminosity class and spectral type. We also compared our results with independent estimates of the spectral type. Cross-checking those results allows us to identify the systematics of the method and to characterise the stellar populations observed by CoRoT. Results: We find that the classification method performs better for stars that were observed during the mission-dedicated photometric ground-based campaigns.The luminosity class is wrong for less than 7% of the targets. Generally, the effective temperature of stars classified as early type (O, B, and A) is overestimated. Conversely, the temperature of stars classified as later type tends to be underestimated. This is mainly due to the adverse effect of interstellar

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Stability of a pair of co-rotating vortices with axial flow

    NASA Astrophysics Data System (ADS)

    Roy, Clément; Schaeffer, Nathanaël; Le Dizès, Stéphane; Thompson, Mark

    2008-09-01

    The three-dimensional linear temporal stability properties of a flow composed of two corotating q-vortices (also called Batchelor vortices) are predicted by numerical stability analysis. As for the corresponding counter-rotating case, when the axial flow parameter is increased, different instability modes are observed and identified as a combination of resonant Kelvin modes of azimuthal wavenumbers m and m +2 within each vortex. In particular, we show that the sinuous mode, which is the dominant instability mode without axial flow, is stabilized in the presence of a moderate axial flow. Different types of mode with a large amplitude in the critical layer are also identified. For small separation distances (above the merging threshold), unstable eigenmodes, corresponding to axial wavenumbers that cannot be easily identified with simple resonant interactions of Kelvin modes, are also observed. Their growth rate is a substantial fraction of the growth rates of low-order resonant modes. The effects of the Reynolds number and vortex separation distance on the growth rate parameter map are considered. Finally, we analyze the similarities and differences between the stability characteristics of co- and counter-rotating vortex pairs.

  12. Rossby autosoliton and stationary model of the Jovian Great Red SPOT

    NASA Astrophysics Data System (ADS)

    Antipov, S. V.; Nezlin, M. V.; Snezhkin, E. N.; Trubnikov, A. S.

    1986-09-01

    A theory proposed about 10 years ago claimed that the jovian Great Red Spot (GRS) was a solitary wave vortex (Rossby soliton) kept stationary by counter-streaming zonal winds. The authors have attempted to verify this soliton theory experimentally. The jovian atmosphere is modelled by a rotating thin parabolic layer of fluid (shallow water) with a free surface in which counter-streaming (zonal) flows are excited mechanically. It is found that instability of these flows can generate a Rossby autosoliton, that is, an undamped stationary solitary vortex which is alone on the perimeter of the system. This result can be considered to support the soliton theory of the GRS.

  13. Topographic Rossby waves in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Hamilton, Peter

    2009-07-01

    Observations of topographic Rossby waves (TRW), using moored current meters, bottom pressure gauges, and Lagrangian RAFOS floats, are investigated for the deep basin of the Gulf of Mexico. Recent extensive measurement programs in many parts of the deep gulf, which were inspired by oil and gas industry explorations into ever deeper water, allow more comprehensive analyses of the propagation and dissipation of these deep planetary waves. The Gulf of Mexico circulation can be divided into two layers with the ∼800-1200 m upper layer being dominated by the Loop Current (LC) pulsations and shedding of large (diameters ∼300-400 km) anticyclonic eddies in the east, and the translation of these LC eddies across the basin to the west. These processes spawn smaller eddies of both signs through instabilities, and interactions with topography and other eddies to produce energetic surface layer flows that have a rich spectrum of orbit periods and diameters. In contrast, current variability below 1000 m often has the characteristics of TRWs, with periods ranging from ∼10-100 days and wavelengths of ∼50-200 km, showing almost depth-independent or slightly bottom intensified currents through the weakly stratified lower water column. These fluctuations are largely uncorrelated with simultaneous upper-layer eddy flows. TRWs must be generated through energy transfer from the upper-layer eddies to the lower layer by potential vorticity adjustments to changing depths of the bottom and the interface between the layers. Therefore, the LC and LC eddies are prime candidates as has been suggested by some model studies. Model simulations have also indicated that deep lower-layer eddies may be generated by the LC and LC eddy shedding processes. In the eastern gulf, the highest observed lower-layer kinetic energy was north of the Campeche Bank under the LC in a region that models have identified as having strong baroclinic instabilities. Part of the 60-day TRW signal propagates towards

  14. Eddy length scales and the Rossby radius in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Nurser, A. J. G.; Bacon, S.

    2013-10-01

    The first (and second) baroclinic deformation (or Rossby) radii are presented and discussed north of ~60° N, focusing on deep basins and shelf seas in the high Arctic Ocean, the Nordic Seas, Baffin Bay, Hudson Bay and the Canadian Arctic Archipelago, derived from high-resolution ice-ocean general circulation model output. Comparison of the model output with measured results shows that low values of the Rossby radius (in shallow water) and high values (in the Canada Basin) are accurately reproduced, while intermediate values (in the region of the Makarov and Amundsen Basins) are overestimated. In the high Arctic Ocean, the first Rossby radius increases from ~5 km in the Nansen Basin to ~15 km in the central Canadian Basin. In the shelf seas and elsewhere, values are low (1-7 km), reflecting weak density stratification, shallow water, or both. Seasonality only strongly impacts the Rossby radii in shallow seas where winter homogenisation of the water column can reduce it to the order of 100 m. We also offer an interpretation and explanation of the observed scales of Arctic Ocean eddies.

  15. Formation and Development of Diabatic Rossby Vortices in a 10-Year Climatology

    DTIC Science & Technology

    2012-06-01

    14. SUBJECT TERMS Diabatic Rossby Vortex, Moist Baroclinic Instability , Explosive Deepening, Composite Analysis Eddy Available Potential Energy...LIST .......................................................................................119  ix LIST OF FIGURES Figure 1.  IR satellite image from... Satellite image of winter storm “Lothar” over Christmas of 1999 (From oiswww.eumetsat.org

  16. Spectral characteristics of Rossby waves in the Northwestern Pacific based on satellite altimetry

    NASA Astrophysics Data System (ADS)

    Belonenko, T. V.; Kubrjakov, A. A.; Stanichny, S. V.

    2016-12-01

    Using satellite altimetry measurement data for 1993-2013, we study the spectral characteristics of Rossby waves in the Northwestern Pacific (25°-50° N, 140°-180° E). For each latitude degree, we draw integral plots of spectral power density calculated with a two-dimensional Fourier transform (2D-FFT). We compare the dispersion equations of Rossby waves calculated from the WKB-approximation and an approximation of a two-layer ocean model with the empirical velocities determined by the slope of isopleths by the Radon method; also, we compare the dispersion equations with the spectral distributions of level variations. It is shown that the main energy of Rossby waves in the Northwestern Pacific corresponds to the first baroclinic mode. At almost all latitudes, there is good agreement between the empirical phase velocities calculated by isopleths by the Radon method and the theoretical values; also, the spectral peaks correspond to graphs of the dispersion equations for the first baroclinic mode Rossby waves, except for the Kuroshio region, where some peaks correspond to the second mode.

  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. Performance of the COROT CCD for high-accuracy photometry

    NASA Astrophysics Data System (ADS)

    Bernardi, P.; Lapeyrere, V.; Buey, J.-T.; Parisot, J.; Schmidt, R.; Leruyet, B.; Tiphène, D.; Gilard, O.; Rolland, G.

    2004-01-01

    The focal plane of the COROT instrument is made of four CCDs, two dedicated to asteroseismology and two dedicated to the detection of telluric planets. The detectors are provided by E2V (4280 series), each having 2k×4k pixels. They work in AIMO and frame transfer mode, at a working temperature of -40°C. As the COROT photometer will have to detect fluctuations expressed in ppm (part per million), a specific calibration of the whole photometric chain has to be achieved. Moreover, we have ten CCDs available and therefore need to calibrate them in order to select four CCDs for the flight focal plane. A specific test bench is dedicated to the calibration of these CCDs, and five have already been tested. The main characteristics of interest are: - cosmetics (black and white pixels or columns): zero white pixels, less than 6 black columns; - pixel response non uniformity (PRNU) versus wavelength: 1% rms at 650 nm. - gain versus temperature: -900 ppm K-1 relative fluctuation - absolute quantum efficiency: 95% max at 650 nm; - quantum efficiency versus temperature: 2000 ppm K-1 relative fluctuation at 650 nm; - full well capacity: 85 to 100 ke-; - dark current at -40°C: <0.5e- pixel-1 sec-1. Comparing the measured characteristics to those provided by E2V, we first check that CCDs meet specifications. Then, when all CCDs are tested, we will select the best CCDs for each scientific program (asteroseismology or planet finding). Specific tools have been developed to compare the performances of the detectors using the images acquired on the test bench and the shapes of the PSF for the two scientific programs. The detectors have also been tested under irradiation; the results strongly depend on the specific orbit of COROT (irradiation dose and related particles) and have to be compared to the global performances of the instrument.

  19. Corotating two-body system of identical Kerr sources

    NASA Astrophysics Data System (ADS)

    Cabrera-Munguia, I.; Ceron, V. E.; López, L. A.; Pedraza, Omar

    2017-09-01

    A binary system of equal corotating Kerr sources is studied after deriving the corresponding 3-parametric asymptotically flat exact solution. Both sources are apart from each other by means of a massless strut (conical singularity). In the context of black holes, the analytical functional form of each horizon σ is expressed in terms of arbitrary Komar physical parameters: mass M, angular momentum J (with parallel spin), and the coordinate distance R. Later on, all the thermodynamical properties related to the horizon are depicted by concise formulae. Finally, the extreme limit case is obtained as a 2-parametric subclass of Kinnersley-Chitre metric.

  20. Non-linear Interactions of Rossby waves in shallow water magnetohydrodynamics on a beta-plane

    NASA Astrophysics Data System (ADS)

    Klimachkov, Dmitry; Petrosyan, Arakel

    2017-04-01

    Rotating magnetohydrodynamic shallow water equations are obtained from conventional magnetohydrodynamic equations for incompressible inviscid heavy plasma layer with free surface in a external vertical magnetic field. The pressure is assumed to be hydrostatic, and the water layer height is considered to be much smaller than horizontal scales. The MHD shallow water equations with an external vertical magnetic field are revised by supplementing them with the equations that are consequences of the magnetic field divergence-free conditions and reveal the existence of third component of the magnetic field in such approximation providing its relation with the horizontal magnetic field. It is shown that the presence of a vertical magnetic field significantly changes the dynamics of the wave processes in astrophysical plasma compared to the neutral fluid and plasma layer in a horizontal magnetic field. We have investigated the interaction of wave packets in the magnetohydrodynamic shallow water flows in external vertical magnetic field and in horizontal (toroidal and poloidal) magnetic field on a β-plane. Linear analysis leads to magneto-Rossby waves in β-plane approximation. In the absence of the horizontal magnetic field the dynamics of plasma appears to be similar to the neutral fluid dynamics. Using the asymptotic multiscale method we obtained the non-linear interaction equations for the waves amplitudes. The analysis of the amplitudes equations shows that on β-plane there are two types of instabilities: one magneto-Rossby wave decays into two magneto-Rossby waves and magneto-Rossby wave amplifies in field of two magneto-Rossby waves. These instabilities occur in both cases: in the external vertical magnetic field and in the horizontal (toroidal and poloidal) magnetic field. For all types of instabilities the growth rates are found.

  1. Equatorially trapped Rossby waves in the presence of meridionally sheared baroclinic flow in the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Chelton, D. B.; Schlax, M. G.; Lyman, J. M.; Johnson, G. C.

    2003-02-01

    TOPEX/POSEIDON altimeter data are analyzed for the 8.5-year period November 1992 to May 2001 to investigate the sea surface height (SSH) and geostrophic velocity signatures of quasi-annual equatorially trapped Rossby waves in the Pacific. The latitudinal structures of SSH and both components of geostrophic velocity are found to be asymmetric about the equator across the entire Pacific with larger amplitude north of the equator. The westward phase speeds are estimated by several different methods to be in the range 0.5-0.6 m s -1. These observed characteristics are inconsistent with the classical theory for first vertical, first meridional mode equatorially trapped Rossby waves, which predicts a phase speed of about 0.9 m s -1 with latitudinally symmetric structures of SSH and zonal velocity and antisymmetric structure of meridional velocity. The observations are even less consistent with the latitudinal structures of SSH and geostrophic velocity components for other modes of the classical theory. The latitudinal asymmetries deduced here have also been consistently observed in past analyses of subsurface thermal data and altimeter data and have been variously attributed to sampling errors in the observational data, a superposition of multiple meridional Rossby wave modes, asymmetric forcing by the wind, and forcing by cross-equatorial southerly winds in the eastern Pacific. We propose a different mechanism to account for the observed asymmetric latitudinal structure of low-frequency equatorial Rossby waves. From the free-wave solutions of a simple 1.5-layer model, it is shown that meridional shears in the mean equatorial current system significantly alter the potential vorticity gradient in the central and eastern tropical Pacific. The observed asymmetric structures of sea surface height and geostrophic velocity components are found to be a natural consequence of the shear modification of the potential vorticity gradient. The mean currents also reduce the predicted

  2. Rossby wave activity in a two-dimensional model - Closure for wave driving and meridional eddy diffusivity

    NASA Technical Reports Server (NTRS)

    Hitchman, Matthew H.; Brasseur, Guy

    1988-01-01

    A parameterization of the effects of Rossby waves in the middle atmosphere is proposed for use in two-dimensional models. By adding an equation for conservation of Rossby wave activity, closure is obtained for the meridional eddy fluxes and body force due to Rossby waves. Rossby wave activity is produced in a climatological fashion at the tropopause, is advected by a group velocity which is determined solely by model zonal winds, and is absorbed where it converges. Absorption of Rossby wave activity causes both an easterly torque and an irreversible mixing of potential vorticity, represented by the meridional eddy diffusivity, K(yy). The distribution of Rossby wave driving determines the distribution of K(yy), which is applied to all of the chemical constituents. This provides a self-consistent coupling of the wave activity with the winds, tracer distributions and the radiative field. Typical winter stratospheric values for K(yy) of 2 million sq m/sec are obtained. Poleward tracer advection is enhanced and meridional tracer gradients are reduced where Rossby wave activity is absorbed in the model.

  3. 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.

  4. Power spectral signatures of interplanetary corotating and transient flows

    NASA Technical Reports Server (NTRS)

    Goldstein, M. L.; Burlaga, L. F.; Matthaeus, W. H.

    1984-01-01

    Studies of the time behavior of the galactic cosmic ray intensity have concluded that long term decreases in the intensity are generally associated with systems of interplanetary flows that contain flare generated shock waves, magnetic clouds and other transient phenomena. The magnetic field power spectral signatures of such flow systems are compared to power spectra obtained during times when the solar wind is dominated by stable corotating streams that do not usually produce long-lived reduction in the cosmic ray intensity. The spectral signatures of these two types of regimes (transient and corotating) are distinct. However, the distinguishing features are not the same throughout the heliosphere. In data collected beyond 1 AU the primary differences are in the power spectra of the magnitude of the magnetic field rather than in the power in the field components. Consequently, decreases in cosmic ray intensity are very likely due to magnetic mirror forces and gradient drifts rather than to small angle scattering due to cyclotron wave-particle interactions.

  5. The CoRoT Mission - Status and Preliminary Results

    NASA Astrophysics Data System (ADS)

    Fridlund, M.

    2007-08-01

    The CoRoT (Convection, Rotation and planetary Transits) space mission is the first dedicated space mission designed to search for exo-planets akin to our own. It is a joint effort by France, Austria Belgium, Brazil, Germany, Spain and the European Space Agency. It is specifically designed to search for exo-planets much smaller than hitherto discovered. It was launched in December 2006 on a mission lasting not less than 3 years. Verification and first operations have proven the mission to superceed all expectations. This is of course most relevant in the fact that planets as small as our own Earth are detectable. In this presentation we describe the experiences of the first 6 mo0nths of the mission, the actual status of the mission, the supporting ground based program, and what we expect in the near future. After giving examples of data relevant to the topic of this session, we turn to describing the expected impact of the results of CoRoT on future endeavours such as KEPLER, Extremely Large Telescopes (ELT's) and ultimately Darwin.

  6. Constraining corotation from shocks in tightly wound spiral galaxies

    NASA Astrophysics Data System (ADS)

    Gittins, D. M.; Clarke, C. J.

    2004-04-01

    We present a new method for estimating the corotation radius in tightly wound spiral galaxies, through analysis of the radial variation of the offset between arms traced by the potential (P-arms) and those traced by dust (D-arms). We have verified the predictions of semi-analytical theory through hydrodynamical simulations and have examined the uniqueness of the galactic parameters that can be deduced by this method. We find that if the range of angular offsets measured at different radii in a galaxy is greater than around π/4, it is possible to locate the radius of corotation to within ~25 per cent. We argue that the relative location of the P- and D-arms provides more robust constraints on the galactic parameters than can be inferred from regions of enhanced star formation (SF-arms), as interpretation of the latter involves uncertainties due to reddening and the assumed star formation law. We thus stress the importance of K-band studies of spiral galaxies.

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

    NASA Astrophysics Data System (ADS)

    COROT Team

    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 Baikonour. 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

  8. 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

  9. Excitation of Rossby waves by HF electromagnetic seismic origin emissions in the earth's mesosphere

    NASA Astrophysics Data System (ADS)

    Tsintsadze, N. L.; Kaladze, T. D.; Tsamalashvili, L. V.

    2009-12-01

    Interaction of high-frequency seismo-electromagnetic emissions with the weakly ionized gas of the ionospheric D-layer is considered. It is shown that through the earth's ionosphere weakly damped high-frequency electron cyclotron electromagnetic waves can propagate. These new type of waves easily reach the ionospheric D-layer where they interact with the existing electrons and ions. Acting on electrons ponderomotive force is taken into account and corresponding modified Charney equation is obtained. It is shown that only nonlinear vortical structures with negative vorticity (anticyclone) can be excited. The amplitude modulation of electromagnetic waves can lead to the excitation of Rossby waves in the weakly ionized gas. The corresponding growth rate is defined. Depending on the intensity of the pumping waves generated by seismic activity different stable and unstable branches of oscillations are found. Detection of the new oscillation branches and energetically reinforcing Rossby solitary vortical anticyclone structures may be serve as precursors to earthquake.

  10. A New Look at the Physics and Energy Fluxes of Rossby Waves

    NASA Astrophysics Data System (ADS)

    Cai, Ming; Huang, Buhua

    2016-04-01

    The presence of the latitudinal variation of the Coriolis parameter serves as a mechanical barrier that causes a mass convergence for the poleward geostrophic flow and divergence for the equatorward flow, just as a sloped bottom terrain does to a crossover flow. Part of the mass convergence causes pressure to rise along the uphill pathway while the remaining part is detoured to cross isobars out of the pathway. This mechanically excited cross-isobar flow, being unbalanced geostrophically, is subject to a "half-cycle" Coriolis force that only turns it to the direction parallel to isobars without continuing to turn it further back to its opposite direction because the geostrophic balance is reestablished once the flow becomes parallel to isobars. Such oscillation, involving a barrier-induced mass convergence, a mechanical deflection, and a half-cycle Coriolis deflection, is referred to as a mechanical-Coriolis oscillation with a "barrier-induced half cycle Coriolis force" as its restoring force. Through a complete cycle of the mechanical-Coriolis oscillation, a new geostrophically balanced flow pattern emerges to the left of the existing flow when facing the uphill (downhill) direction of the barrier in the North(Southern) Hemisphere. The β-barrier is always sloped towards the pole in both hemispheres, responsible for the westward propagation of Rossby waves. The identification of the physical oscillation mechanism for Rossby waves enables us to recover the well-known "missing" term in energy flux of Rossby waves and reconcile the apparent inconsistency between pressure work and group velocity of Rossby waves.

  11. Rossby Wave Instability of Thin Accretion Disks. II. Detailed Linear Theory

    SciTech Connect

    Li, H.; Finn, J. M.; Lovelace, R. V. E.; Colgate, S. A.

    2000-04-20

    In an earlier work we identified a global, nonaxisymmetric instability associated with the presence of an extreme in the radial profile of the key function L(r){identical_to}({sigma}{omega}/{kappa}{sup 2})S{sup 2/{gamma}} in a thin, inviscid, nonmagnetized accretion disk. Here {sigma}(r) is the surface mass density of the disk, {omega}(r) is the angular rotation rate, S(r) is the specific entropy, {gamma} is the adiabatic index, and {kappa}(r) is the radial epicyclic frequency. The dispersion relation of the instability was shown to be similar to that of Rossby waves in planetary atmospheres. In this paper, we present the detailed linear theory of this Rossby wave instability and show that it exists for a wider range of conditions, specifically, for the case where there is a ''jump'' over some range of r in {sigma}(r) or in the pressure P(r). We elucidate the physical mechanism of this instability and its dependence on various parameters, including the magnitude of the ''bump'' or ''jump,'' the azimuthal mode number, and the sound speed in the disk. We find a large parameter range where the disk is stable to axisymmetric perturbations but unstable to the nonaxisymmetric Rossby waves. We find that growth rates of the Rossby wave instability can be high, {approx}0.2{omega}{sub K} for relative small jumps or bumps. We discuss possible conditions which can lead to this instability and the consequences of the instability. (c) 2000 The American Astronomical Society.

  12. The Relative Frequency of Rossby Wave Train Triggering Mechanisms Associated with Downstream Development Over Europe

    DTIC Science & Technology

    2014-06-01

    Because Rossby waves are zonally limited in their scale, Lee and Held (1993) describe a “packet of wave activity” propagating on the mean zonal ...exchanges with the mean zonal flow of the jet. Kew et al. (2010) equate a PV anomaly with a relative vorticity maximum at upper-levels and state it is...Montgomery 2004). BW13 show that with sufficient intensity, the cyclonic circulation associated with the DRV can penetrate to the tropopause and provoke

  13. Simple Methods to Extract Analytical Solutions for Rossby Waves on Continuously Stratified Zonal Background Flows

    NASA Astrophysics Data System (ADS)

    Vianna, M. L.

    2016-02-01

    Observed westward phase speeds of Rossby waves in a subtropical region dominated by stratified eastward jets in the South Indian Ocean are about five times the traditional linear theory for propagation of Rossby waves in a stratified ocean. To date no simple analytical generalization of the standard dispersion relation with the inclusion of the effect of baroclinic eastward currents has been obtained, even for flat surface and bottom boundary conditions. One reason may be due to a kind of entanglement between the vertical profile of the jet and the phase speed eigenvalue, which makes this a nonlinear albeit separable eigenvalue problem even for linear theory. A quasi-exact entangled solution, separable by a Modified Bessel Transform, makes possible simple generalizations of the standard dispersion relation, away from critical layers. An interesting application of the method to Rossby waves over the South Indian Coutercurrent at 26° S using a parabolic approximation to the zonal velocity around its minimum at 500 m is offered here. The phase speed enhancement γ =c/c0, where c is the eigenvalue of the vertical velocity and c0 the phase speed given by the standard theory for the first baroclinic mode depends on a single parameter s=(π 2/12)U{zz(β N2/f2)-1, where Uzz is the curvature of the vertical profile of the mean zonal velocity. For (s/γ )≥{1} , the enhancement is simply given by γ = s2/3 , while for (s/γ )≤{1} , γ = 1+s . Examples near the critical layer and wavelengths of the order of the mean local Rossby radius (baroclinic instability) is also discussed in this context. The effects of adding sharp mid-oceanic ridges to the boundary conditions are also discussed.

  14. On Long Baroclinic Rossby Waves in the Tropical North Atlantic Observed From Profiling Floats

    DTIC Science & Technology

    2007-05-16

    coastline. Unstable standing Rossby waves with annual and semiannual periods are shown in both the subbasins. All unstable waves, decaying , radiate shorter...42] The bin average produced a new sampling repre- senting a set of smoothed velocities related to centers of float clusters embedded into...computations (Figures 4b–4d) demonstrate frequent changes in the structure of the perturbations associated with their merger, decay , and dissipation and that the

  15. Impact of rossby waves on surface chlorophyll patterns in the north atlantic ocean

    NASA Astrophysics Data System (ADS)

    Charria, G.; Dadou, I.; Sudre, J.; Garçon, V.

    2003-04-01

    In situ measurements (Price and Magaard, 1986 ; Spall, 1992) and sea surface height anomaly measured by Topex/Poseidon and ERS2 (Cromwell, 2001 ; Cipollini et al. , 1997, 1998) have allowed to detect baroclinic Rossby waves in the North Atlantic and to study their features (wavelength, group and phase speed and period). Enhancement of surface chlorophyll-a by Rossby waves has been recently detected by several authors in ocean color data (Uz et al., 2001 ; Cipollini et al., 2001; Charria et al., 2002). The monthly SeaWiFS data and combined TOPEX/ERS2 data over the 5 years 1998-2002 are used. Detecting this wave in altimetry and ocean color data is difficult due to the weak signal compared to the seasonal cycle and the mesoscale activity. A spatial filter, based on a wavelet analysis, has been used to highlight this wave in the North Atlantic. We will discuss, in space and time, the link between Rossby waves and mesoscale activity as well as the interannuality of these waves, both on the physical signal (sea surface anomaly) and the biological signal (surface chlorophyll). The zonal "waveguide" at 34°N will be specially investigated.

  16. Unstable interaction of gravity-inertial waves with Rossby waves with application to solar system atmospheres

    NASA Astrophysics Data System (ADS)

    McKenzie, J. F.; Doyle, T. B.

    2010-01-01

    This letter reports on the important features of an analysis of the combined theory of gravity - inertial - Rossby waves on a β-plane in the Boussinesq approximation. In particular, it is shown that the coupling between higher frequency gravity - inertial waves and lower frequency Rossby waves, arising from the accumulated influences of the β effect, stratification characterized by the Väisäla - Brunt frequency N, the Coriolis frequency f, and the component of vertical propagation wave number kz , may lead to an unstable coupling between buoyancy - inertial modes with westward propagating Rossby waves. “Supersonic” fast rotators (such as Jupiter) are predicted to be unstable in a fairly narrow band of latitudes around their equators. The Earth is moderately supersonic and exhibits instability within about 34° of its equator. Slow “subsonic” rotators (e.g. Mercury, Venus, and the Sun's corona) are unstable at all latitudes except those very close to the poles where the β effect vanishes.

  17. Three-dimensional slow Rossby waves in rotating spherical density-stratified convection

    NASA Astrophysics Data System (ADS)

    Elperin, T.; Kleeorin, N.; Rogachevskii, I.

    2017-09-01

    We develop a theory of three-dimensional slow Rossby waves in rotating spherical density stratified convection. The Rossby waves, with frequencies which are much smaller than the rotating frequency, are excited by a nonaxisymmetric instability from the equilibrium based on the developed convection. These waves interact with the inertial waves and the density stratified convection. The density stratification is taken into account using the anelastic approximation for very low-Mach-number flows. We study long-term planetary Rossby waves with periods which are larger than two years. We suggest that these waves are related to the southern oscillation and El Niño. The El Niño is an irregularly periodical variation in winds and sea surface temperatures over the tropical Pacific ocean, while the southern oscillation is an oscillation in surface air pressure between the tropical eastern and the western Pacific ocean. The strength of the southern oscillation is characterized by the southern oscillation index (SOI). The developed theory is applied for the interpretation of the observed periods of the SOI. This study demonstrates a good agreement between the theoretical predictions and the observations.

  18. 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.

  19. North American Drought and Links to Northern Eurasia: The Role of Stationary Rossby Waves

    NASA Technical Reports Server (NTRS)

    Wang, Hailan; Schubert, Siegfried D.; Koster, Randal D.

    2017-01-01

    This chapter provides an overview of the role of stationary Rossby waves in the sub-seasonal development of warm season drought over North America and subsequent downstream development of climate anomalies over northern Eurasia. The results are based on a case study of a stationary Rossby wave event that developed during 20 May 15 June 1988. Simulations with the NASA Goddard Earth Observing System (GEOS-5) atmospheric general circulation model highlight the importance of the mean jet streams in guiding and constraining the path and speed of wave energy propagation. In particular, convective anomalies that developed over the western Pacific in late May (in the presence of the strong North Pacific jet) produce a predilection for persistent upper-level high anomalies over central North America about ten days later, leading to the rapid development of severe dry conditions there. There are indications of continued downstream wave energy propagation that reaches northern Eurasia about two weeks later, leading to the development of dry conditions over eastern Europe and western Russia, and cool and wet conditions over western Europe and central northern Eurasia. The results suggest that stationary Rossby waves can serve as a source of predictability for sub-seasonal development of droughts over North America and northern Eurasia.

  20. Corotation lag of Saturn's magnetosphere - Global ionospheric conductivities revisited

    NASA Technical Reports Server (NTRS)

    Cheng, Andrew F.; Waite, J. H., Jr.

    1988-01-01

    In view of the recent publication of Eviatar and Richardson (1986), who have calculated the Pedersen conductance of Saturn's ionosphere to be much smaller than previous estimates, the Pedersen conductance is recalculated using the same neutral atmosphere model as these authors. The results confirm the earlier estimates that the ionospheric Pedersen conductance of Saturn's ionosphere ranges from 0.3 to 17 mho near the terminator as a function of latitude. The source of discrepancy appears to be the inclusion by Eviatar and Richardson of ion density into the ion-neutral collision frequency term, which is incorrect. Contrary to the conclusion of Eviatar and Richardson, Saturn's ionospheric Pedersen conductance is high enough to impose nearly perfect corotation between the ionosphere and the magnetosphere.

  1. 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.

  2. 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.

  3. (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).

  4. Astrossismologia e o satélite COROT

    NASA Astrophysics Data System (ADS)

    Andrade, L. B. P.; Janot Pacheco, E.

    2003-08-01

    Este trabalho centra-se em atividades na fase de pré-lançamento do satélite COROT, da agência espacial francesa (CNES), a ser lançado em 2005. O satélite será dedicado à sismologia estelar e à procura de exoplanetas. Nosso programa de trabalho centra-se em dois pontos principais: (1) efetuar uma procura detalhada nos campos COROT de alvos astrofísicos de especial interesse; (2) participar das análises espectroscópicas prévias de alvos selecionados para determinação de parâmetros físicos das estrelas com a maior precisão possível. Na presente etapa, priorizou-se o primeiro ponto do projeto. Foi feito um levantamento geral dos objetos astrofísicos encontrados nos dois campos de observação, centrados em 06H50M e 18H50M, com raios de 10 minutos. Concluiu-se que as estrelas B-Be deverão ser observadas no campo sismológico, enquanto que as anãs brancas deverão sê-lo no campo exoplanetário. Objetos a serem observados foram escolhidos de forma a estarem próximos de alvos principais dos programas centrais do satélite. Paralelamente, estudos e pesquisas bibliográficas foram feitos para compreender os assuntos de interesse principal, ou seja, as pulsações não-radiais de estrelas Ob-Be

  5. 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

  6. 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.

  7. Transiting exoplanets from the CoRoT space mission. VII. The ``hot-Jupiter''-type planet CoRoT-5b

    NASA Astrophysics Data System (ADS)

    Rauer, H.; Queloz, D.; Csizmadia, Sz.; Deleuil, M.; Alonso, R.; Aigrain, S.; Almenara, J. M.; Auvergne, M.; Baglin, A.; Barge, P.; Bordé, P.; Bouchy, F.; Bruntt, H.; Cabrera, J.; Carone, L.; Carpano, S.; de La Reza, R.; Deeg, H. J.; Dvorak, R.; Erikson, A.; Fridlund, M.; Gandolfi, D.; Gillon, M.; Guillot, T.; Guenther, E.; Hatzes, A.; Hébrard, G.; Kabath, P.; Jorda, L.; Lammer, H.; Léger, A.; Llebaria, A.; Magain, P.; Mazeh, T.; Moutou, C.; Ollivier, M.; Pätzold, M.; Pont, F.; Rabus, M.; Renner, S.; Rouan, D.; Shporer, A.; Samuel, B.; Schneider, J.; Triaud, A. H. M. J.; Wuchterl, G.

    2009-10-01

    Aims: The CoRoT space mission continues to photometrically monitor about 12 000 stars in its field-of-view for a series of target fields to search for transiting extrasolar planets ever since 2007. Deep transit signals can be detected quickly in the “alarm-mode” in parallel to the ongoing target field monitoring. CoRoT's first planets have been detected in this mode. Methods: The CoRoT raw lightcurves are filtered for orbital residuals, outliers, and low-frequency stellar signals. The phase folded lightcurve is used to fit the transit signal and derive the main planetary parameters. Radial velocity follow-up observations were initiated to secure the detection and to derive the planet mass. Results: We report the detection of CoRoT-5b, detected during observations of the LRa01 field, the first long-duration field in the galactic anti-center direction. CoRoT-5b is a “hot Jupiter-type” planet with a radius of 1.388+0.046-0.047 R_Jup, a mass of 0.467+0.047-0.024 M_Jup, and therefore, a mean density of 0.217+0.031-0.025 g cm-3. The planet orbits an F9V star of 14.0 mag in 4.0378962 ± 0.0000019 days at an orbital distance of 0.04947+0.00026-0.00029 AU. Observations made with SOPHIE spectrograph at the Observatoire de Haute Provence (07B.PNP.MOUT), France, and HARPS spectrograph at ESO La Silla Observatory (072.C-0488(E), 082.C-0312(A)), and partly based on observations made at the Anglo-Australian Telescope. The CoRoT space mission, launched on December 27, 2006, was developed and is operated by CNES, with the contribution of Austria, Belgium, Brasil, ESA, Germany, and Spain.

  8. How to diagnose the horizontal flux of mesoscale / Rossby eddy energy in the extension regions of western boundary currents?

    NASA Astrophysics Data System (ADS)

    Aiki, H.

    2014-12-01

    There have been few studies on the horizontal flux of energy associated with mesoscale eddies and Rossby eddies. (Many studies in the past decade are on either energy conversions or the flux-divergence of eddy energy). This is partly attributed to the fact that, in general, the pressure flux in the traditional eddy energy equation does not look in the direction of the group velocity of Rossby waves. This has been a limitation in the understanding of the maintenance mechanism of the extension of western boundary currents (WBCs). The present study has developed a new eddy energy equation which (is independent of the quasi-geostrophic approximation but) allows us to diagnose the horizontal flux of eddy / wave energy with retaining the direction of the group velocity of a wide-array of Rossby-wave types. The types of Rossby waves include that are associated with both pure and equivalent beta effects, namely variants of Rossby waves concerning the horizontal gradient of (i) planetary vorticity, (ii) relative vorticity associated with mean currents (which is as in atmospheric dynamics), and (iii) the background stratification (which is associated with the slope of thermocline and yields an effect similar to topographic Rossby waves). A diagnosis of an idealised experiment shows that, in the regions of the extension of WBCs, the effects (ii) and (iii) prevail over the effect (i) to yield the eastward flux of eddy / wave energy. The result is that the total westward flux of eddy / wave energy by an array of Rossby-wave types may sometimes cancel out the eastward flux of eddy / wave energy owing to advection by mean currents in the extension regions.

  9. 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

  10. 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.

  11. Rossby wave errors and the gradient of PV at the tropopause

    NASA Astrophysics Data System (ADS)

    Harvey, B. J.

    2016-12-01

    The isentropic gradient of potential vorticity (PV) at the tropopause is typically weaker in global numerical weather forecasts than in corresponding analyses. The average gradient declines with lead time and tends towards a steady value dependent on resolution. Here the consequences of this systematic model error on the dynamics of Rossby waves are explored using a simple toy model. The approach taken is to analyse Rossby waves on a slightly-smoothed PV front, or `step', in a single-layer quasi-geostrophic model. Smoothing the PV front has two notable effects: the zonal phase speed of waves decreases and the ability of wave activity to disperse meridionally increases (the waveguide becomes more `lossy').The decrease in phase speed is the result of a leading-order compensation between a decrease in jet speed and a decrease in wave propagation speed, with the jet speed decrease dominating at second order in the width of the gradient. Estimates are made for the phase speed error associated with the difference in width of the tropopause zone between analyses and 5-day forecasts. The smoother tropopause in the forecast results in phase speeds that are too low by 1 m/s, which over a 5-day period amounts to a phase error of 400 km, and group speeds that are too low by 2 m/s.The increase in the ability of wave activity to disperse meridionally is attributed to enhanced filamentation of PV when the tropopause is smoother and, via the conservation of wave activity, results in a transient decay of wave amplitude. As such, there is a dynamical mechanism by which numerical diffusion acting on the sharp gradient of PV at the tropopause can act to reduce the amplitude of large-scale Rossby waves. This result has implications for the understanding of forecast errors in NWP models and biases in climate models.

  12. Detection, dynamics and climatology of Rossby wave initiation on the extratropical waveguide

    NASA Astrophysics Data System (ADS)

    Röthlisberger, Matthias; Martius, Olivia; Wernli, Heini

    2016-04-01

    Synoptic-scale Rossby waves are ubiquitous in the extratropical flow and, together with jets and vortices, they form the building blocks of extratropical dynamics. In this study a novel method is presented that automatically identifies the initiation of synoptic-scale Rossby waves (RWIs) on tropopause-level waveguides. RWIs are identified based on geometry changes of the 2 Potential Vorticity Units (PVU) contours on isentropic levels. The 2 PVU contours are hereby regarded as proxies for the position and shape of the extratropical waveguide. A RWI is recorded in a zonally aligned (i.e. wave-free) longitudinal contour segment if the segment becomes wavy over time and, additionally, the respective 2 PVU contour is wave-free upstream of the segment. The algorithm is applied to the ERA-Interim data set to compile a Northern Hemisphere climatology of RWIs (1979-2013) on tropopuase-level waveguides. To further illustrate the potential of the method, an example RWI is presented in which a wave is initiated by a mesoscale lower stratospheric high-PV anomaly interacting with the extratropical jet and with surface baroclinicity. Next, the spatial distribution and seasonal cycle of RWIs is discussed. The majority of the RWIs occur over the Northwestern Pacific and a secondary initiation region is located over the North Atlantic. Especially the initiation region over the North Pacific undergoes a strong seasonal cycle, both in its location and in the number of RWIs occurring. Finally, we present a composite view on RWIs occurring over the North Pacific and highlight key aspects of the dynamics of the first stage in the life cycle of synotic-scale Rossby waves.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Structure, stability, and evolution of 3D Rossby vortices in protoplanetary disks

    NASA Astrophysics Data System (ADS)

    Richard, S.; Barge, P.; Le Dizès, S.

    2013-11-01

    Context. Large-scale persistent vortices could play a key role in the evolution of protoplanetary disks, particularly in the dead zone where no turbulence associated with a magnetic field is expected. These vortices are known to form easily in 2D disks via the Rossby wave or the baroclinic instability. In three dimensions, however, their formation and stability is a complex problem and still a matter of debate. Aims: We study the formation of vortices by the Rossby wave instability in a stratified inviscid disk and describe their 3D structure, stability, and long-term evolution. Methods: Numerical simulations were performed using a fully compressible hydrodynamical code based on a second-order finite volume method. We assumed a perfect-gas law and a non-homentropic adiabatic flow. Results: The Rossby wave instability is found to proceed in 3D in a similar way as in 2D. Vortices produced by the instability look like columns of vorticity in the whole disk thickness; the weak vertical motions are related to the weak inclination of the vortex axis that appears during the development of the RWI. Vortices with aspect ratios higher than 6 are unaffected by the elliptical instability. They relax into a quasi-steady columnar structure that survives hundreds of rotations while slowly migrating inward toward the star at a rate that reduces with the vortex aspect ratio. Vortices with a lower aspect ratio are by contrast affected by the elliptic instability. Short aspect ratio vortices (χ < 4) are completely destroyed in a few orbital periods. Vortices with an intermediate aspect ratio (4 < χ < 6) are partially destroyed by the elliptical instability in a region away from the midplane where the disk stratification is sufficiently strong. Conclusions: Elongated Rossby vortices can survive many orbital periods in protoplanetary disks in the form of vorticity columns. They could play a significant role in the evolution of the gas and the gathering of solid particles to form

  19. The Three-Dimensional Structure of Breaking Rossby Waves in the Polar Wintertime Stratosphere.

    NASA Astrophysics Data System (ADS)

    Polvani, L. M.; Saravanan, R.

    2000-11-01

    The three-dimensional nature of breaking Rossby waves in the polar wintertime stratosphere is studied using an idealized global primitive equation model. The model is initialized with a well-formed polar vortex, characterized by a latitudinal band of steep potential vorticity (PV) gradients. Planetary-scale Rossby waves are generated by varying the topography of the bottom boundary, corresponding to undulations of the tropopause. Such topographically forced Rossby waves then propagate up the edge of the vortex, and their amplification with height leads to irreversible wave breaking.These numerical experiments highlight several nonlinear aspects of stratospheric dynamics that are beyond the reach of both isentropic two-dimensional models and fully realistic GCM simulations. They also show that the polar vortex is contorted by the breaking Rossby waves in a surprisingly wide range of shapes.With zonal wavenumber-1 forcing, wave breaking usually initiates as a deep helical tongue of PV that is extruded from the polar vortex. This tongue is often observed to roll up into deep isolated columns, which, in turn, may be stretched and tilted by horizontal and vertical shears. The wave amplitude directly controls the depth of the wave breaking region and the amount of vortex erosion. At large forcing amplitudes, the wave breaking in the middle/lower portions of the vortex destroys the PV gradients essential for vertical propagation, thus shielding the top of the vortex from further wave breaking.The initial vertical structure of the polar vortex is shown to play an important role in determining the characteristics of the wave breaking. Perhaps surprisingly, initially steeper PV gradients allow for stronger vertical wave propagation and thus lead to stronger erosion. Vertical wind shear has the notable effect of tilting and stretching PV structures, and thus dramatically accelerating the downscale stirring. An initial decrease in vortex area with increasing height (i.e., a

  20. 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.

  1. 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.

  2. Dynamics of quasi 2D co-rotating vortex merger

    NASA Astrophysics Data System (ADS)

    Khandekar, Akshay G.

    Merger of vortices is examined experimentally to compare the merger of slender parallel vortices generated coincidentally. It is known that like-sign vortices rotate around a common center of circulation and merger between the vortices may occur under certain conditions. This merger is dependent on the strength of the vortex circulation, distance of separation between the centers of the two vortices, ReGamma, and vorticity distribution. Quasi-2D experimental data is examined and merger relations are derived. The 2D experiments conducted in a vortex generator tank uses high aspect ratio rotating paddles. The vortex merger tank generates slender co-rotating vortices and are examined using PIV (Particle Image Velocimetry). Merger characteristics are compared at centerline, 25% span and 5% span for different circulation strengths. Symmetric and asymmetric mergers are studied and it is found that in both cases, the vortex pair rotates around an axis perpendicular to the plane of the vortex pair. Symmetric merger is seen to occur at the center between the two vortices whereas in asymmetric merger the stronger vortex breaks the weaker vortex filaments and continues to follow its path. Wall effects seem to have an effect of vortex braiding and vortex stretching. Closer to the wall, the merger time increases while the merged vortex dissipates faster than at the centerline.

  3. 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.

  4. 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.}

  5. A Study of Co-Rotating Wake Vortex Instabilities

    NASA Astrophysics Data System (ADS)

    Bristol, Robert; Savas, Omer

    2000-11-01

    Observations of an instability between pairs of co-rotating wake vortices produced from a flapped airfoil are presented. Data from particle imaging velocimetry and flow-visualization show the growth of a periodic disturbance on the weaker vortex, leading to merger of the two vortices in approximately one orbit. The instability grows in a plane inclined at 45 degrees with respect to the line connecting the two vortices, suggesting that it is driven by the straining field of the stronger vortex acting upon the weaker one. A linear stability analysis of the problem is presented, which is a generalization of the Crow theory, covering the case for an unequal pair of vortices. Within the confines of this analysis, the straining field emerges as the primary mechanism for instability, with the effects of self-rotation and orbit-induced rotation acting together to stabilize the pair. However, the linear theory fails to reproduce the experimental results, most likely because of strong interactions due to the close proximity of the finite-size vortices. Finally, results are shown from the spectral Navier-Stokes solver in cylindrical co-ordinates of Marcus et. al., which produces instabilities similar to the ones observed experimentally. Circulation-based Reynolds numbers for the experiments reach 300,000 while those for the simulations reach 60,000.

  6. Dynamical corotation torques on low-mass planets

    NASA Astrophysics Data System (ADS)

    Paardekooper, S.-J.

    2014-11-01

    We study torques on migrating low-mass planets in locally isothermal discs. Previous work on low-mass planets generally kept the planet on a fixed orbit, after which the torque on the planet was measured. In addition to these static torques, when the planet is allowed to migrate it experiences dynamical torques, which are proportional to the migration rate and whose sign depends on the background vortensity gradient. We show that in discs a few times more massive than the minimum-mass solar nebula, these dynamical torques can have a profound impact on planet migration. Inward migration can be slowed down significantly, and if static torques lead to outward migration, dynamical torques can take over, taking the planet beyond zero-torque lines set by saturation of the corotation torque in a runaway fashion. This means that the region in non-isothermal discs, where outward migration is possible, can be larger than what would be concluded from static torques alone.

  7. Elemental Abundances in Corotating Interaction Regions at High Solar Latitudes

    NASA Astrophysics Data System (ADS)

    Maclennan, C. G.; Lanzerotti, L. J.

    1995-04-01

    Throughout 1993, as the Ulysses spacecraft traveled from ˜23° to ˜45° south heliolatitude, the HI-SCALE instrument on the spacecraft measured a recurrent series of enhanced particle fluxes with a recurrence period of ˜26.5 days. These particles are accelerated from a background seed population by the corotating interaction regions (CIRs) associated with a southern solar polar coronal hole. Using the Wart detector telescope of the HI-SCALE instrument, we have analyzed the elemental abundances of C, N, O, and Fe relative to He for 0.5 4.0 MeV/nucl ions and Ne, Mg, and Si for 1.0 4.0 MeV/nucl ions in the CIRs. We compare the relative abundances to some previous measurements reported from 1 A.U. as well as with solar photosphere abundances. We note that HI-SCALE measurements of the heliolatitude dependence of the oxygen abundance and spectrum as reported by Lanzerottiet al. (1994) suggest that a substantial fraction of the seed population for the CIR-accelerated oxygen is likely to be the anomalous oxygen component of the cosmic rays.

  8. Simulating binary inspirals in a corotating spherical coordinate system

    NASA Astrophysics Data System (ADS)

    Garrett, Travis Marshall

    The gravitational waves produced by the inspiral and merger of two black holes are expected to be the first detected by the newly constructed gravitational wave observatories. Accurate theoretical models that describe the generation and shape of these gravitational waves need to be constructed. These theoretical waveforms will aid in the detection of astrophysical wave sources, and will allow us to test general relativity in the strong field regime. Numerical relativity is the leading candidate for constructing accurate waveforms, and in this thesis we develop methods to help advance the field. In particular we use a corotating spherical coordinate system to simulate the evolution of a compact binary system as it produces gravitational radiation. We combine this method with both the Weak Radiation Reaction and Hydro-without- Hydro approximations to produce stable dynamical evolutions. We also utilize Nordström's conformally flat theory of gravitation as a relativistic laboratory during the development process. Additionally we perform semi-analytic calculations to determine the approximate way in which binaries decay in Nordström's theory. We find an excellent agreement between our semi-analytic calculations and the orbital evolutions produced by the code, and thus conclude that these methods form a solid basis for simulating binary inspirals and the gravitational waves they produce in general relativity.

  9. 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.

  10. NON-BAROTROPIC LINEAR ROSSBY WAVE INSTABILITY IN THREE-DIMENSIONAL DISKS

    SciTech Connect

    Lin, Min-Kai

    2013-03-10

    Astrophysical disks with localized radial structure, such as protoplanetary disks containing dead zones or gaps due to disk-planet interaction, may be subject to the non-axisymmetric Rossby wave instability (RWI) that leads to vortex formation. The linear instability has recently been demonstrated in three-dimensional (3D) barotropic disks. It is the purpose of this study to generalize the 3D linear problem to include an energy equation, thereby accounting for baroclinity in three dimensions. Linear stability calculations are presented for radially structured, vertically stratified, geometrically thin disks with non-uniform entropy distribution in both directions. Polytropic equilibria are considered but adiabatic perturbations assumed. The unperturbed disk has a localized radial density bump, making it susceptible to the RWI. The linearized fluid equations are solved numerically as a partial differential equation eigenvalue problem. Emphasis on the ease of method implementation is given. It is found that when the polytropic index is fixed and adiabatic index increased, non-uniform entropy has negligible effect on the RWI growth rate, but pressure and density perturbation magnitudes near a pressure enhancement increase away from the midplane. The associated meridional flow is also qualitatively changed from homentropic calculations. Meridional vortical motion is identified in the nonhomentropic linear solution, as well as in a nonlinear global hydrodynamic simulation of the RWI in an initially isothermal disk evolved adiabatically. Numerical results suggest that buoyancy forces play an important role in the internal flow of Rossby vortices.

  11. 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.

  12. Heat transport in low-Rossby-number Rayleigh-Bénard convection.

    PubMed

    Julien, Keith; Knobloch, Edgar; Rubio, Antonio M; Vasil, Geoffrey M

    2012-12-21

    We demonstrate, via simulations of asymptotically reduced equations describing rotationally constrained Rayleigh-Bénard convection, that the efficiency of turbulent motion in the fluid bulk limits overall heat transport and determines the scaling of the nondimensional Nusselt number Nu with the Rayleigh number Ra, the Ekman number E, and the Prandtl number σ. For E < 1 inviscid scaling theory predicts and simulations confirm the large Ra scaling law Nu-1 ≈ C(1)σ(-1/2)Ra(3/2)E(2), where C(1) is a constant, estimated as C(1) ≈ 0.04 ± 0.0025. In contrast, the corresponding result for nonrotating convection, Nu-1 ≈ C(2)Ra(α), is determined by the efficiency of the thermal boundary layers (laminar: 0.28 ≤ α ≤ 0.31, turbulent: α ~ 0.38). The 3/2 scaling law breaks down at Rayleigh numbers at which the thermal boundary layer loses rotational constraint, i.e., when the local Rossby number ≈ 1. The breakdown takes place while the bulk Rossby number is still small and results in a gradual transition to the nonrotating scaling law. For low Ekman numbers the location of this transition is independent of the mechanical boundary conditions.

  13. 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.

  14. MAGNETIC ROSSBY WAVES IN THE SOLAR TACHOCLINE AND RIEGER-TYPE PERIODICITIES

    SciTech Connect

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

    2010-02-01

    Apart from the eleven-year solar cycle, another periodicity around 155-160 days was discovered during solar cycle 21 in high-energy solar flares, and its presence in sunspot areas and strong magnetic flux has been also reported. This periodicity has an elusive and enigmatic character, since it usually appears only near the maxima of solar cycles, and seems to be related with a periodic emergence of strong magnetic flux at the solar surface. Therefore, it is probably connected with the tachocline, a thin layer located near the base of the solar convection zone, where a strong dynamo magnetic field is stored. We study the dynamics of Rossby waves in the tachocline in the presence of a toroidal magnetic field and latitudinal differential rotation. Our analysis shows that the magnetic Rossby waves are generally unstable and that the growth rates are sensitive to the magnetic field strength and to the latitudinal differential rotation parameters. Variation of the differential rotation and the magnetic field strength throughout the solar cycle enhance the growth rate of a particular harmonic in the upper part of the tachocline around the maximum of the solar cycle. This harmonic is symmetric with respect to the equator and has a period of 155-160 days. A rapid increase of the wave amplitude could give rise to a magnetic flux emergence leading to observed periodicities in solar activity indicators related to magnetic flux.

  15. 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.

  16. Nonlinear Saturation of Topographically Forced Rossby Waves in a Barotropic Model.

    NASA Astrophysics Data System (ADS)

    Giannitsis, Constantine; Lindzen, Richard S.

    2001-10-01

    A quasigeostrophic barotropic model is used to examine the nonlinear saturation of forced Rossby waves and the role of wave-wave interactions in limiting the wave growth. A simple mechanism, based on wave interference, is used to produce strong transient eddy growth and an analytical linear solution for the flow evolution is used as a starting point. Given the rigid upper bound on wave growth, set by the potential enstrophy conservation principle, the linear solution is bound to break down at high forcing amplitudes. An analytical quasi-linear solution, which guarantees potential enstrophy conservation, is formulated and its domain of validity is examined with a numerical nonlinear model. The nonlinear flow evolution is shown to bear strong similarity to the analytical quasi-linear solution and wave-mean flow interactions are found to be always sufficient to limit wave growth. The saturation of the forced disturbances is shown to come through the deceleration of the mean flow and the modification of the topographic vorticity forcing. Overall, wave-wave interactions prove not to be important in the saturation process in the examples considered. While the authors consider the implications of this result for the observationally more relevant case of vertically propagating Rossby waves, explicit calculations are clearly called for.

  17. Seasonal Evolution of Rossby and Gravity Wave Induced Laminae in Ozonesonde Data Obtained from Wallops Island, Virginia

    NASA Technical Reports Server (NTRS)

    Pierce, R. Bradley; Grant, William B.

    1998-01-01

    A method for evaluating the seasonal evolution of ozone laminae using ozonesonde data is discussed. The method uses the correlation between small-scale ozone and potential temperature variations to distinguish between laminae generated by quasi-isentropic filamentation by Rossby waves and by vertical displacements of material surfaces by gravity waves. Data from Wallops Island, Virginia show that Rossby wave induced ozone laminae are most frequently encountered at Wallops during the winter months near 15 km while statistically significant gravity wave induced laminae occur above 15 km during the early winter and at the tropopause from late winter through early spring.

  18. 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.

  19. Interface structure of co-rotating interaction regions

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Roelof, E. C.; Forsyth, R. J.

    1997-01-01

    Plasma and particle observations on Ulysses during its passes through the southern and northern heliosphere have revealed that, inside the streamer belt, the large-scale structure of the quiet global heliosphere is dominated by corotating interaction regions (CIRs). Therefore, considerable attention is now being given to the internal plasma structure of CIRs, and in particular, to the manifestations of the stream interfaces that should mark their origins as interactions between low speed solar wind (in the low-latitude streamer belt) and high speed solar wind (from the equatorial extensions of the high latitude polar coronal holes). The SWICS and HI-SCALE experiments on Ulysses combine plasma and energetic particle measurements that are of considerable utility for such studies because, between them, they cover the proton energy range from 10 eV to 5 MeV. These measurements are used, together with magnetic field data, to study the remarkable series of CIRs that occurred during the period beginning July 1992 and the end of 1993 as Ulysses rose from the ecliptic to a southern heliographic latitude of 48 deg. The structure of the regions between the forward and reverse shocks were previously analyzed in terms of the proton specific entropy argument log that should exhibit a discontinuous jump at the stream interface. It was claimed that the stream interface, defined with respect to specific entropy, is also associated with a discontinuity in energetic proton intensities. The energetic particle data (greater than 60 keV) and how they were ordered with respect to interfaces and with respect to the magnetic field were examined.

  20. 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.

  1. Existence of a component corotating with the earth in high-latitude disturbance magnetic fields

    NASA Technical Reports Server (NTRS)

    Suzuki, A.; Kim, J. S.; Sugiura, M.

    1982-01-01

    A study of the data from the high-latitude North American IMS network of magnetic stations suggests that there is a component in substorm perturbations that corotates with the earth. It is as yet not certain whether the existence of this component stems from the corotation of a part of the magnetospheric plasma involved in the substorm mechanism or if it is a 'phase change' resulting from the control of the substorm manifestations by the earth's main magnetic field which is not axially symmetric. There are other geophysical phenomena showing a persistence of longitudinal variations corotating with the earth. These phenomena are of significance for a better understanding of ionosphere-magnetosphere coupling.

  2. 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

  3. Variability of the central-North Atlantic subtropical gyre induced by Rossby waves

    NASA Astrophysics Data System (ADS)

    Vélez-Belchí, P.; Kwon, Y. O.; Yang, J.; Pérez-Hernández, M. D.; Hernandez-Guerra, A.

    2014-12-01

    The Atlantic Ocean meridional overturning circulation (AMOC) contributes to moderate of climate in Europe through the northward transport of 25% of the global heat flux, which is at maximum at around 24.50ºN. Consequently, transatlantic oceanographic sections at this latitude have become a benchmark for monitoring long-term changes in the Atlantic and to study the nature and causes of climate change. This has resulted in the occupation of the North Atlantic Ocean hydrographic transect along 24.5ºN seven times since 1957, more than any other transoceanic section in the world. The east-west slope in the dynamic height at 200dbar referenced to 1800dbar along 24.5ºN has decreased in 12-cm between 1957 and 2011, suggesting a spin-down of the central-North Atlantic subtropical gyre. Over imposed on this long-term trend in the slope there is a decadal variability in the slope with amplitudes up to 5 cm, that persist for several years, as the one during 2001-2004 that preceded large compensated changes in temperature and salinity at 24.5ºN. The hydrographic dataset show that this signal is predominantly due to vertical motion of the isopycnal surfaces, extending to depths of at least 1800 dbar. Using the linearized equations for a stratified ocean separated into vertical modes and for low-frequency, large-scale wind forcing, we explore the role of westward propagating linear Rossby waves in explaining these long-term and decadal changes. The results indicate the long-term change may be explained by the differential trend of wind stress curl between the eastern and western basins. The results are compared with simulations from a two-layer primitive equation model with realistic topography. Given the recent interests in Rossby waves, as the main mechanism explaining the observed seasonal cycle of the AMOC, an analysis of the impact of the seasonal variability induced by Rossby waves at 24.5ºN is also carried out.

  4. 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.

  5. The study of Be stars with the CoRoT satellite

    NASA Astrophysics Data System (ADS)

    Diago, P. D.; Gutierrez-Soto, J.; Fabregat, J.; Suso, J.; COROT Be Team

    2011-11-01

    The CoRoT space mission, launched in December 2006, is a spacecraft devoted to the study of the stellar interiors and the exo-planet search. Concerning the seismology of the Be stars, the presence of pulsations in late-type Be stars is still a matter of controversy. It constitutes an important issue to establish the relationship between non-radial pulsations and the mass-loss mechanism in Be stars. In this field, the CoRoT satellite is providing data with an unprecedent quality and precision that is confirming non-radial pulsations in Be stars. The CoRoT Be Team is an international collaboration composed by members from France, Spain, Brazil and Belgium and is in charge of the exploitation and analysis of the Be stars data. In this work we present the highlighted results of the observed Be stars by CoRoT and the future prospects of the CoRoT Be Team. These results include the detection of the Be star HD 49 330 during an outburst phase and the measurement of the change in the oscillation spectrum during this rare event. These observations gave insight into the nature of the explosion. It will help to solve a question that has been pending for years: are oscillations the cause of the outbursts? Moreover, for the first time, the CoRoT satellite has detected simultaneously the rotational and the pulsational frequencies for the Be star HD 50 209, which constitutes a proof of the presence of pulsations in the Be stars. %J Highlights of Spanish Astrophysics VI, Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society (SEA), held in Madrid, September 13 - 17, 2010, Eds.: M. R. Zapatero Osorio, J. Gorgas, J. Maiz Apellaniz, J. R. Pardo, and A. Gil de Paz., p. 531-531

  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. 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.

  8. VizieR Online Data Catalog: Corot photometry of TYC 455-791-1 (Strassmeier+, 2017)

    NASA Astrophysics Data System (ADS)

    Strassmeier, K. G.; Granzer, T.; Mallonn, M.; Weber, M.; Weingrill, J.

    2016-11-01

    From the original CoRoT white-light flux obtained on two consecutive runs, we filter out obvious outliers from the SAA (south Atlantic Anomaly). The third column are the remaining CoRoT data points. The two data set were merged using individual zero-points of 716386.54e- for the first data set and 721882.56e- for the second data set, respectively. The magnitudes thus calculates are in column four. The last column is the combined model of the transit plus a 12th order Fourier-series fit to the out-of-transit data. (1 data file).

  9. Pioneer 10 and 11 observations of waves upstream of interplanetary corotating shocks

    NASA Technical Reports Server (NTRS)

    Bavassano, Bruno; Smith, Edward J.; Tsurutani, Bruce T.

    1987-01-01

    An extended region of enhanced magnetic field fluctuations is found upstream of some of the corotating shocks observed by Pioneer 10 and Pioneer 11 between 1 and 5 AU. This perturbed region is present when the corotating shock, generally quasi-perpendicular, becomes oblique or quasi-parallel due to a temporary out-of-spiral direction of the upstream magnetic field. The observed waves are almost not compressional. Their amplitude is a large fraction of the ambient field, and their frequency is around 1 mHz in the spacecraft frame. A brief discussion of the possible mechanisms of generation is given.

  10. 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.

  11. CoRoT archive as a treasury of variable stars

    NASA Astrophysics Data System (ADS)

    Benko, Jozsef M.; Paparo, Margit

    2015-08-01

    The CoRoT satellite supported the scientific community by a huge data base of variable stars. The investigation of RR Lyrae stars (radially pulsating classical variable stars of high amplitude), especially benefit the continuous space data, due to long periodicity. The CoRoT RR Lyrae stars were intensively discussed in numerous papers in the last few years, but the latest runs have not been checked for finding RR Lyrae stars up to now. We found eight new RR Lyrae stars that we investigated for the lately localized characteristics of Blazhko RR Lyrae stars: the period doubling and additional modes. We present the preliminary results here.

  12. 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.

  13. Observations of Planetary Mixed Rossby-Gravity Waves in the Upper Stratosphere.

    NASA Astrophysics Data System (ADS)

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

    1990-12-01

    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 Limb Infrared Monitor of the Stratosphere (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° 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 s1. 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.

  14. Effect of basic state on seasonal variation of convectively coupled Rossby wave

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Chen, Lin

    2017-03-01

    Convectively coupled equatorial Rossby (ER) waves display maximum varability over the northern hemisphere during boreal summer and over the southern hemisphere during boreal winter. It suggests that the seasonal variation of ER waves is significantly affected by the annual cycle of basic state. However, which specific environmental factor plays a determining role remains obscure. This study investigates the background influence on the seasonal variation of ER wave by employing an intermediate anomaly atmospheric model. By prescribing boreal summer/winter seasonal mean state as the model's basic state, the authors found that the model is able to simulate the trapping of the ER wave purtrubation over the northern/southern hemisphere as in observation. Further sensitivity experiments suggest that the moisture distribution plays a major role in modulating the ER wave structure while the mosoonal flows play a minor role.

  15. 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.

  16. 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.

  17. Rossby Wave Breaking and its Relationship with Climate and Ozone Stratosphere-Troposphere Exchange

    NASA Astrophysics Data System (ADS)

    Jing, P.; Patel, M.

    2016-12-01

    One of the challenges in the study of climate change impacts is that the dynamical response of the atmosphere to climate change is not well understood. Rossby wave breaking (RWB) is an important dynamical process that is associated with stratosphere-troposphere exchange (STE). This study investigates the effect of climate change on RWB using potential vorticity (PV) fields from the NASA Modern-Era Retrospective Analysis for Research and Application (MERRA) between 1986 and 2015. The long-term trend of RWB on isentropic surfaces in the upper tropospheric and lower stratospheric (UTLS) region in terms of its frequency, location, and intensity is analyzed. The relationship of RWB to high tropospheric ozone events is also investigated by employing NASA satellite observed ozone data from the Microwave Limb Sounder (MLS) and Ozone Monitoring Instrument (OMI) as well as ozonesonde measurements.

  18. Impact of the gravity of a Schwarzschild black hole upon the Rossby wave instability

    NASA Astrophysics Data System (ADS)

    Casse, F.; Varniere, P.; Meliani, Z.

    2017-01-01

    In an early work, the Rossby wave instability was proposed to explain the variability thought to originate in the close vicinity of black holes but this was done in the pseudo-Newtonian approach. Here we present the first general relativistic (GR) hydrodynamics simulations of this instability not only proving its theorized existence in a full GR environment but also studying the effect of the strong gravity on the instability. To that end, we performed a set of simulations increasingly closer to the black hole with our new GR version of the MPI-AMRVAC code. This allows us to study the minute changes in the behaviour of the instability. We found that a pseudo-Newtonian approach gives adequate results provided that the time-shifting induced by the black hole gravity is taken into account. Hence, to view the disc as a distant observer would, a full GR ray-tracing post-treatment of the simulations is a must.

  19. The numerical calculation of rotating fluid flows at low Rossby numbers

    NASA Astrophysics Data System (ADS)

    Page, M. A.

    Numerical methods which can be used to calculate flows in a rapidly rotating fluid are presented. The flows considered are those within a closed cylindrical container rotating about an axis aligned with the sidewalls, with a slow motion superposed upon the rigid rotation of the fluid. The Rossby number in this case is small; the Eckman number is also considered to be small, so that viscous diffusion is confined to the thin layers of the fluid. The flows calculated are those in the geostrophic region of the fluid, where the motion is depth-independent and the governing equations are two-dimensional. Between the geostatic flow and the walls of the container, however, there are ageostrophic layers of two types. By analyzing these layers theoretically, appropriate boundary conditions on the geostrophic flow can be calculated.

  20. Vortex Rossby wave propagation in baroclinic tropical cyclone-like vortices

    NASA Astrophysics Data System (ADS)

    Gao, Cen; Zhu, Ping

    2016-12-01

    This study extends the vortex Rossby wave (VRW) propagation theory into baroclinic tropical cyclone-like vortices. Dispersion relation, group velocities, and stagnation radius/height of propagating wave packets in baroclinic conditions are derived using the Wenzel-Kramers-Brillouin approximation. It is found that the VRW dispersion relation in baroclinic vortices in isentropic coordinates has the same mathematical form as that in barotropic vortices in pseudoheight coordinates. However, baroclinicity causes the vertical wave number to increase as wave packets propagate upward, resulting in different wave propagation features from those in barotropic vortices. The stagnation radius and level are constrained by a "critical" surface where the initial central angular phase velocity equals the angular velocity of the vortex. Depending on the specific structure of vortex basic-state baroclinicity and positions where asymmetries are located, the excited waves can either be trapped vertically and behave like those in barotropic conditions or effectively propagate upward but with their radial propagation largely suppressed.

  1. Rossby wave breaking, the upper level jet, and serial clustering of extratropical cyclones in western Europe

    NASA Astrophysics Data System (ADS)

    Priestley, Matthew D. K.; Pinto, Joaquim G.; Dacre, Helen F.; Shaffrey, Len C.

    2017-01-01

    Winter 2013/14 was the stormiest on record for the UK and was characterized by recurrent clustering of extratropical cyclones. This clustering was associated with a strong, straight and persistent North Atlantic jet and was also associated with Rossby wave breaking (RWB) on both flanks, pinning the jet in place. The occurrence of RWB and cyclone clustering is further studied in 36 years of the ERA-Interim Reanalysis. Clustering at 55°N is associated with an extended and anomalously strong eddy-driven jet flanked on both sides by RWB. However, clustering at 65(45)°N has a dominance of RWB to the south (north) of the jet, deflecting the jet northward (southward). A positive correlation was found between clustering and RWB occurrence to the north and south of the jet. However, there is considerable spread in these relationships.

  2. 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.

  3. 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

  4. Generation of the North Equatorial Undercurrent Jets by Triad Baroclinic Rossby Wave Interactions (Invited)

    NASA Astrophysics Data System (ADS)

    Qiu, B.; Chen, S.; Sasaki, H.; Rudnick, D. L.

    2013-12-01

    Formation processes responsible for the North Equatorial Undercurrent (NEUC) jets that appear across the tropical North Pacific Ocean near 9N, 13N, and 18N, are explored both theoretically and using numerical models with different complexities. Analyses of an eddy-resolving global ocean general circulation model output reveal that the NEUC jets have a mode-1 baroclinic vertical structure and are spatially persistent on the interannual and longer time scales. This OGCM-simulated vertical structure prompts us to adopt the simpler, nonlinear 1.5-layer reduced-gravity model, as well as the baroclinic Rossby wave triad interaction theory, to unravel the essential processes underlying the NEUC jets. The seed for the NEUC jets originates in annual baroclinic Rossby waves driven by the large-scale surface wind stress forcing. Emanating from the ocean basin's eastern boundary, these wind-forced ``primary'' waves are subject to nonlinear triad interactions and break down offshore where the e-folding timescale of the most unstable triad instability matches the advective timescale of the primary waves. The break-down boundary of the wind-forced primary waves tends to tilt northeast-southwestward and, west of this boundary, finite-amplitude eddies emerge, whose meridional scales are set by the most unstable short secondary waves participating in the triad interactions along the break-down boundary. With their meridional scales set similarly by the short secondary waves, the time-mean zonal jets of characteristics resembling the observed NEUC jets are formed by the converging potential vorticity fluxes of these finite-amplitude eddies.

  5. 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

  6. 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.

  7. A climatology of Rossby wave generation in the middle atmosphere of the Southern Hemisphere from MERRA reanalysis

    NASA Astrophysics Data System (ADS)

    Rodas, Claudio; Pulido, Manuel

    2017-09-01

    A climatological characterization of Rossby wave generation events in the middle atmosphere of the Southern Hemisphere is conducted using 20 years of Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis. An automatic detection technique of wave generation events is developed and applied to MERRA reanalysis. The Rossby wave generation events with wave period of 1.25 to 5.5 days and zonal wave number from one to three dominate the Eliassen-Palm flux divergence around the stratopause at high latitudes in the examined 20 year period. These produce an eastward forcing of the general circulation between May and mid-August in that region. Afterward from mid-August to the final warming date, Rossby wave generation events are still present but the Eliassen-Palm flux divergence in the polar stratopause is dominated by low-frequency Rossby waves that propagate from the troposphere. The Rossby wave generation events are associated with potential vorticity gradient inversion, and so they are a manifestation of the dominant barotropic/baroclinic unstable modes that grow at the cost of smearing the negative meridional gradient of potential vorticity. The most likely region of wave generation is found between 60° and 80°S and at a height of 0.7 hPa, but events were detected from 40 hPa to 0.3 hPa (which is the top of the examined region). The mean number of events per year is 24, and its mean duration is 3.35 days. The event duration follows an exponential distribution.

  8. A deeper view of the CoRoT-9 planetary system. A small non-zero eccentricity for CoRoT-9b likely generated by planet-planet scattering

    NASA Astrophysics Data System (ADS)

    Bonomo, A. S.; Hébrard, G.; Raymond, S. N.; Bouchy, F.; Lecavelier des Etangs, A.; Bordé, P.; Aigrain, S.; Almenara, J.-M.; Alonso, R.; Cabrera, J.; Csizmadia, Sz.; Damiani, C.; Deeg, H. J.; Deleuil, M.; Díaz, R. F.; Erikson, A.; Fridlund, M.; Gandolfi, D.; Guenther, E.; Guillot, T.; Hatzes, A.; Izidoro, A.; Lovis, C.; Moutou, C.; Ollivier, M.; Pätzold, M.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.

    2017-07-01

    CoRoT-9b is one of the rare long-period (P = 95.3 days) transiting giant planets with a measured mass known to date. We present a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with CoRoT and Spitzer. Combining our new data with already published measurements we redetermine the CoRoT-9 system parameters and find good agreement with the published values. We uncover a higher significance for the small but non-zero eccentricity of CoRoT-9b () and find no evidence for additional planets in the system. We use simulations of planet-planet scattering to show that the eccentricity of CoRoT-9b may have been generated by an instability in which a 50 M⊕ planet was ejected from the system. This scattering would not have produced a spin-orbit misalignment, so we predict that the CoRoT-9b orbit should lie within a few degrees of the initial plane of the protoplanetary disk. As a consequence, any significant stellar obliquity would indicate that the disk was primordially tilted.

  9. CoRoT-2a Magnetic Activity: Hints for Possible Star-Planet Interaction

    NASA Astrophysics Data System (ADS)

    Pagano, Isabella; Lanza, Antonino F.; Leto, Giuseppe; Messina, Sergio; Barge, Pierre; Baglin, Annie

    2009-09-01

    CoRoT-2a is a young (≈0.5 Gyr) G7V star accompanied by a transiting hot-Jupiter, discovered by the CoRoT satellite (Alonso et al. Astron Astrophys 482:L21, 2008; Bouchy et al. Astron Astrophys 482:L25, 2008). An analysis of its photospheric activity, based on spot modelling techniques previously developed by our group for the analysis of the Sun as a star, shows that the active regions on CoRoT-2a arised within two active longitudes separated by about 180° and rotating with periods of 4.5221 and 4.5543 days, respectively, at epoch of CoRoT observations (112 continous days centered at ≈2007.6). We show that the total spotted area oscillates with a period of about 28.9 days, a value close to 10 times the synodic period of the planet with respect to the active longitude pattern rotating in 4.5221 days. Moreover, the variance of the stellar flux is modulated in phase with the planet orbital period. This suggests a possible star-planet magnetic interaction, a phenomenon already seen in other extrasolar planetary systems hosting hot-Jupiters.

  10. The intimate relation between the low T/W instability and the corotation point

    NASA Astrophysics Data System (ADS)

    Passamonti, A.; Andersson, N.

    2015-01-01

    We study the low T/W instability associated with the f mode of differentially rotating stars, where T and W are, respectively, the kinetic and gravitational energy of the star. Our stellar models are described by a polytropic equation of state and the rotation profile is given by the standard j-constant law. The properties of the relevant oscillation modes, including the instability growth time, are determined from time evolutions of the linearized dynamical equations in Newtonian gravity. In order to analyse the instability we monitor also the canonical energy and angular momentum. Our results demonstrate that the l = m = 2 f mode becomes unstable as soon as a corotation point develops inside the star (i.e. whenever there is a point where the mode's pattern speed matches the bulk angular velocity). Considering various degrees of differential rotation, we show that the instability grows faster deep inside the corotation region and deduce an empirical relation that correlates the mode frequency and the star's parameters, which captures the main features of the l = m = 2 f-mode growth time. This function is proportional to the product of the kinetic to gravitational energy ratio and the gradient of the star's spin, strengthening further the relationship between the corotation point and the low T/W instability. We briefly consider also the l = m = 2 r mode and demonstrate that it never moves far inside the corotation region even for significant differential rotation.

  11. 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.

  12. 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

  13. 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

  14. On the role of corotation radius in the low T/W dynamical instability of differentially rotating stars

    NASA Astrophysics Data System (ADS)

    Yoshida, Shin'ichirou; Saijo, Motoyuki

    2017-04-01

    We investigate the nature of so-called low T/W dynamical instability in a differentially rotating star, by focusing on the role played by the corotation radius of the unstable oscillation modes. A one-dimensional model of linear perturbation, which neglects dependence of variables on the coordinate along the rotational axis of the star, is solved to obtain stable and unstable eigenmodes. A linear eigenmode having a corotation radius, at which azimuthal pattern speed of the mode coincides with the stellar angular velocity, is categorized to either a complex (growing or damping) mode or a purely real mode belonging to a continuous spectrum of frequency. We compute canonical angular momentum and its flux to study eigenmodes with corotation radius. In a dynamically unstable mode, sound wave transports its angular momentum in such a way that the absolute value of the angular momentum is increased on both sides of the corotation radius. We further evaluate growth of amplitude of reflected sound wave incident to a corotation point, and find that the overreflection of the wave and the trapping of it between the corotation radius and the surface of the star may qualitatively explain dependences of eigenfrequencies on the stellar differential rotation. The results suggest that the low T/W instability may be caused by overreflection of sound waves trapped mainly between the surface of the star and a corotation radius.

  15. Two Scales of Mixed Rossby-gravity and Kelvin Waves in the lower Stratosphere

    NASA Astrophysics Data System (ADS)

    Trenberth, K. E.; Karl, T. R.; Xie, S. P.; Nieves, V.; Tung, K. K.; Roemmich, D. H.; Kiladis, G. N.; Gehne, M.; Dias, J.

    2015-12-01

    Two scales of mixed Rossby-gravity (MRG) and Kelvin waves in the lower stratosphere are identified through space time spectral, cross spectral and Principal Component analysis of filtered dynamical fields from radiosonde and reanalysis data. A standard covariance matrix EOF analysis of filtered wind along the equator at 50 hPa is used to isolate MRG and Kelvin waves, using ERA Interim analyses for the entire period 1979-2012. This approach uses 2-6 day meridional wind for MRG waves and 10-25 day eastward zonal wind for Kelvin waves as a basis for the two independent EOF analyses, respectively. Raw wind, geopotential height and CLAUS brightness temperature are then projected onto the EOF PCs at all levels from 1000 to 1 hPa to obtain the structure and evolution of the waves. In all cases EOF pairs are obtained corresponding to propagating modes. The classical Yanai MRG waves are readily identified, and have periods of around 4 days and zonal wavenumber four meridional wind and streamfunction structures centered on the equator, with antisymmetric zonal wind and geopotential as expected. However a faster mode, with a period of around three days is also identified, with a zonal wavenumber three structure. This latter mode is actually much more coherent in cross spectra between antisymmetric zonal wind, geopotential and temperature at 10 degrees north and south. This scale matches the equatorial Rossby radius expected of a disturbance with an equivalent depth of about 120 meters, as identified in space-time spectra of various dynamical quantities obtained from lower stratospheric radiosonde and reanalyses. Strong modulation of this MRG activity by the QBO is also seen for both modes. Kelvin waves are similarly identified using equatorial zonal wind filtered for 10-25 day eastward travelling fluctuations. Two scales are evident here: a wave one and also a wave two disturbance, each with periods of around 14 days. Evidence that the Kelvin and MRG modes are excited by

  16. 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.

  17. 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.

  18. Limits to the presence of transiting circumbinary planets in CoRoT Data

    NASA Astrophysics Data System (ADS)

    Klagyivik, P.; Deeg, H. J.; Cabrera, J.; Csizmadia, Sz.; Almenara, J. M.

    2017-06-01

    Aims: During its flight phase, from 2007-2012, the CoRoT mission delivered light curves for over 2000 eclipsing binaries. Data from the Kepler mission have proven the existence of several transiting circumbinary planets. While light curves from CoRoT typically have lower precision and shorter coverage, the number of CoRoT targets is similar to that of Kepler and some of the known circumbinary planets could potentially be detected in CoRoT data as well. The aim of this work was to reanalyse the entire CoRoT Data set to search for the presence of circumbinary planets and to derive limits on the abundances of such planets. Methods: We developed a code that removes the signatures of eclipsing binaries from the light curves, and searches for quasi-periodic, transit-like features in the light curves after removal of binary eclipses and instrumental features. The code requires little information on sample systems and can also be used for other space missions, such as Kepler, K2, TESS, and PLATO. The code is broad in the requirements leading to detections, but was tuned to deliver an amount of detections that are manageable in a subsequent, mainly visual, assessment of their origin. Results: We identified three planet candidates in the CoRoT sample whose transits would have arisen from a single pass across the central binary; however, no candidates with transit events from multiple planetary orbits remained. We calculated the upper limits for the number of Jupiter, Saturn-, and Neptune-sized planets in co-planar orbits for different orbital period ranges. We found that there are much fewer giant planets in short periodic orbits around close binary systems than around single stars. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A117

  19. Improved variability classification of CoRoT targets with Giraffe spectra

    NASA Astrophysics Data System (ADS)

    Sarro, L. M.; Debosscher, J.; Neiner, C.; Bello-García, A.; González-Marcos, A.; Prendes-Gero, B.; Ordieres, J.; León, G.; Aerts, C.; de Batz, B.

    2013-02-01

    Aims: We present an improved method for automated stellar variability classification, using fundamental parameters derived from high resolution spectra, with the goal to improve the variability classification obtained using information derived from CoRoT light curves only. Although we focus on Giraffe spectra and CoRoT light curves in this work, the methods are much more widely applicable. Methods: In order to improve the variability classification obtained from the photometric time series, only rough estimates of the stellar physical parameters (Teff and log (g)) are needed because most variability types that overlap in the space of time series parameters, are well separated in the space of physical parameters (e.g. γ Dor/SPB or δ Sct/β Cep). In this work, several state-of-the-art machine learning techniques are combined to estimate these fundamental parameters from high resolution Giraffe spectra. Next, these parameters are used in a multi-stage Gaussian-Mixture classifier to perform an improved supervised variability classification of CoRoT light curves. The variability classifier can be used independently of the regression module that estimates the physical parameters, so that non-spectroscopic estimates derived e.g. from photometric colour indices can be used instead. Results: Teff and log (g) are derived from Giraffe spectra, for 6832 CoRoT targets. The use of those parameters in addition to information extracted from the CoRoT light curves, significantly improves the results of our previous automated stellar variability classification. Several new pulsating stars are identified with high confidence levels, including hot pulsators such as SPB and β Cep, and several γ Dor-δ Sct hybrids. From our samples of new γ Dor and δ Sct stars, we find strong indications that the instability domains for both types of pulsators are larger than previously thought. The CoRoT space mission, launched on 27 December 2006, has been developed and is operated by CNES, with

  20. 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

    2016-04-14

    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.

  1. Impact of ENSO on seasonal variations of Kelvin Waves and mixed Rossby-Gravity Waves

    NASA Astrophysics Data System (ADS)

    Rakhman, Saeful; Lubis, Sandro W.; Setiawan, Sonni

    2017-01-01

    Characteristics of atmospheric equatorial Kelvin waves and mixed Rossby-Gravity (MRG) waves as well as their relationship with tropical convective activity associated with El Niño-Southern Oscillation (ENSO) were analyzed. Kelvin waves and MRG waves were identified by using a Space-Time Spectral Analysis (STSA) technique, where the differences in the strength of both waves were quantified by taking the wave spectrum differences for each ENSO phase. Our result showed that Kelvin wave activity is stronger during an El Nino years, whereas the MRG wave activity is stronger during the La Nina years. Seasonal variations of Kelvin wave activity occurs predominantly in MAM over the central to the east Pacific in the El Nino years, while the strongest seasonal variation of MRG wave activity occus in MAM and SON over the northern and southern Pacific during La Nina years. The local variation of Kelvin wave and MRG wave activities are found to be controlled by variation in lower level atmospheric convection induced by sea surface temperature in the tropical Pacific Ocean.

  2. 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.

  3. 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.

  4. Global normal-mode Rossby waves observed in stratospheric ozone data

    SciTech Connect

    Randel, W.J. )

    1993-02-01

    Westward-propagating Rossby normal-mode planetary waves are documented in stratospheric ozone data using Solar Backscatter Ultraviolet (SBUV) satellite measurements. These modes are evidenced by enhanced spectral power and near-global coherence for westward-traveling zonal wave 1 oscillations with periods of 5-10 days. The ozone waves have maxima in high latitudes of the middle stratosphere (due to transport) and over midlatitudes in the upper stratosphere (due to photochemistry). These modes are nearly continuous throughout the eight years of SBUV observations, with maximum global coherence during the equinoxes. The upper-stratospheric waves are symmetric (in phase) between hemispheres, even for modes previously identified as antisymmetric in geopotential height. This behavior is due to differing wave vertical structure in each hemisphere: the planetary temperature waves are nearly in phase in the upper stratosphere, even though the height waves are out of phase. The observed ozone waves are furthermore compared to calculations based on linear wave transport and photochemistry, incorporating derived wind and temperature fields. Good agreement is found, showing that normal modes provide an idealized context to study the linear wave behavior of trace constituents in the real atmosphere. 23 refs., 17 figs.

  5. The behavior of magnetic Prandtl number on the Rossby wave instability in the protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Gholipour, Mahmoud; Ebadi, Hossein; Shaji, Zeynab

    2017-07-01

    In recent years, the Rossby wave instability (RWI) has become the target of intense theoretical and simulation investigations in dealing to some ambiguous problems such as the planet formation and angular momentum transport in the protoplanetary discs. The role of hydrodynamic turbulence on the RWI theory has been well understood by many theoretical and simulation works. However, less attention has been paid to the magnetohydrodynamic (MHD) turbulence in theoretical works related to the RWI. However, the turbulent magnetic Prandtl numbers (Prm), i.e., the ratio of the turbulent viscosity to the turbulent magnetic diffusivity, is one of the significant parameters in (MHD) turbulence. On the other hand, the gradient and strength of the toroidal magnetic field can affect some variables and parameters in the stationary and perturbation states in some radii which may be lead to important results. In this paper, the whole range of Prm is considered in details with considering the gradient and strength of the toroidal magnetic field. Although complicating the problem, it gives us a comprehensive view on the RWI occurrence in the cold and hot discs. The results show that the Prm can significantly control the RWI occurrence as well as the growth rate of unstable modes. While the magneto-rotational instability cannot be responsible for the angular momentum transport in the protoplanetary discs, our results indicate that the RWI is responsible about this subject in these discs.

  6. A New Look at the Physics of Rossby Waves: A Mechanical-Coriolis Oscillation

    NASA Astrophysics Data System (ADS)

    Cai, M.; Huang, B.

    2012-12-01

    The presence of the latitudinal variation of the Coriolis parameter serves as a mechanical barrier that causes a mass convergence for the poleward geostrophic flow and divergence for the equatorward flow, just as a sloped bottom terrain does to a crossover flow. Part of the mass convergence causes pressure to rise along the uphill pathway while the remaining part is detoured to cross isobars out of the pathway. This mechanically excited cross-isobar flow, being unbalanced geostrophically, is subject to a "half-cycle" Coriolis force that only turns it to the direction parallel to isobars without continuing to turn it further back to its opposite direction because the geostrophic balance is reestablished once the flow becomes parallel to isobars. Such oscillation, involving a barrier-induced mass convergence, a mechanical deflection, and a half-cycle Coriolis deflection, is referred to as a mechanical-Coriolis oscillation with a "barrier-induced half-cycle Coriolis force" as its restoring force. Through a complete cycle of the mechanical-Coriolis oscillation, a new geostrophically balanced flow pattern emerges to the left of the existing flow when facing the uphill (downhill) direction of the barrier in the North (Southern) Hemisphere. The β-barrier is always sloped towards the pole in both hemispheres, responsible for the westward propagation of Rossby waves.

  7. Convection-driven kinematic dynamos at low Rossby and magnetic Prandtl numbers

    NASA Astrophysics Data System (ADS)

    Calkins, Michael A.; Long, Louie; Nieves, David; Julien, Keith; Tobias, Steven M.

    2016-12-01

    Most large-scale planetary magnetic fields are thought to be driven by low Rossby number convection of a low magnetic Prandtl number fluid. Here kinematic dynamo action is investigated with an asymptotic, rapidly rotating dynamo model for the plane layer geometry that is intrinsically low magnetic Prandtl number. The thermal Prandtl number and Rayleigh number are varied to illustrate fundamental changes in flow regime, ranging from laminar cellular convection to geostrophic turbulence in which an inverse energy cascade is present. A decrease in the efficiency of the convection to generate a dynamo, as determined by an increase in the critical magnetic Reynolds number, is observed as the buoyancy forcing is increased. This decreased efficiency may result from both the loss of correlations associated with the increasingly disordered states of flow that are generated, and boundary layer behavior that enhances magnetic diffusion locally. We find that the spatial characteristics of the large-scale magnetic field is dependent only weakly on changes in flow behavior. In contrast, the behavior of the small-scale magnetic field is directly dependent on, and therefore shows significant variations with, the small-scale convective flow field. However, our results are limited to the linear, kinematic dynamo regime; future simulations that include the Lorentz force are therefore necessary to assess the robustness of these results.

  8. Dual behavior of the toroidal magnetic field versus the Rossby wave instability

    NASA Astrophysics Data System (ADS)

    Gholipour, Mahmoud

    2016-12-01

    The Rossby wave instability (RWI) theory has been considered as one of the top topics in astrophysics due to the fact that it deals with some ambiguous questions, such as the angular momentum transport in the poorly ionized regions of the protoplanetary discs. Based on the theoretical and simulation works, two important factors in the study of the RWI are the viscosity and magnetic field, which are directly connected to each other because the large-scale toroidal magnetic fields are produced by the magnetohydrodynamic (MHD) turbulence. Therefore, it is essential to consider more details about the toroidal magnetic field both in the steady state and perturbation state. In this paper, the role of the strength and gradient of the toroidal magnetic field is investigated on the RWI at the dead zone in the regions of bump. The obtained results show that the gradient of the toroidal magnetic field or its strength have a major role in the RWI occurrence, which have received relatively less attention in previous works. Also, the role of the gradient of the toroidal magnetic field in the RWI is important even in the weak magnetic fields. Hence, the obtained results are very different from what we previously expected, and it seems crucial to research and develop this issue in the theoretical and simulation works. This paper can be helpful on the study of the angular momentum transport in the cold accretion discs, such as accretion discs in quiescent dwarf novae or around the white-dwarf primary.

  9. The relationship between mixed Rossby-gravity waves and convection in a general circulation model

    NASA Technical Reports Server (NTRS)

    Hess, Peter G.; Hendon, Harry H.; Battisti, David S.

    1993-01-01

    We investigate the relationship between mixed Rossby-gravity waves (MRGWs) and convection in a general circulation model. The experiments described are performed in a general circulation model with the lower boundary set to that of an ocean surface everywhere. Several experiments are run varying the convective parameterization scheme (using either a modified Kuo scheme or a moist convective adjustment scheme) and varying the tropical sea surface temperatures (specified to be zonally symmetric in all cases), thereby changing the location of the modeled intertropical convergence zones (ITCZs). The appearance of a robust MRGW occurs when the sea surface temperature is such that two ITCZs straddle the equator. The particular sea surface temperature distribution used and the parameterization scheme for convection also affect the structure and strength of the modeled MRGW. The vertical structure of MRGWs is analyzed in the experiment in which this wave mode is the most energetic. We show that MRGWs of several different zonal length scales exist in the troposphere in association with convection; however, it is only the longer length scales which can be discerned in the upper troposphere and lower stratosphere.

  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. 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

  12. 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.

  13. Nonlinear effects near the particle resonance

    NASA Astrophysics Data System (ADS)

    Palous, J.

    1980-07-01

    The nonlinear behavior of stellar orbits near the particle resonance is described. For the rotation speed of the spiral structure the value of 20 km/s per kpc is used which was derived elsewhere (Palous et al., 1977). This new value draws attention to the orbits approaching the corotation from the distant peripheries of the stellar system. These orbits exhibit near the damped particle resonance a leap-frogging motion. The maximum of the response density is near the points L1 and L2 and it is slightly shifted in the direction opposite to that of galactic rotation.

  14. 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

  15. Direct computation of the sound from a compressible co-rotating vortex pair

    NASA Technical Reports Server (NTRS)

    Mitchell, Brian E.; Lele, Sanjiva K.; Moin, Parviz

    1992-01-01

    The far-field sound from corotating vortices is computed by direct computation of the unsteady, compressible Navier-Stokes equations on a computational mesh that extends to two acoustic wavelengths in all directions. The vortices undergo a period of corotation followed by a sudden merger. A 2D version of Moehring's equation is developed and used in conjunction with source terms computed in the simulation to predict the far-field sound. The prediction agrees with the simulation to within 3 percent. Results of far-field pressure fluctuations for an acoustically noncompact case are also presented for which the prediction is 66 percent too high. Results also indicate that the monopole contribution of 'viscous sound' is negligible for this flow.

  16. CoRoT observations of the young open cluster Dolidze 25

    NASA Astrophysics Data System (ADS)

    Ripepi, V.; Leccia, S.; Baglin, A.; Ruoppo, A.; Bernabei, S.; Zwintz, K.; Cusano, F.; Gandolfi, D.; Guenter, E. W.; Alencar, S.; Marconi, M.; Monteiro, M. J. P. F. G.; Palla, F.; Alcalá, J. M.; Boehm, T.; Catala, C.; Chavero, C.; Corradi, W. S.; Degl'Innocenti, S.; de La Reza, R.; Deluil, M.; Favata, F.; Fernandez, M.; Gregorio-Hetem, J.; Lepine, J. D. R.; Pinheiro, F. J. G.; Prada Moroni, P. G.; Quast, G.; Torres, C. A. O.; Weiss, W.

    2010-07-01

    We present some preliminary results based on the CoRoT observations of the young distant cluster Dolidze 25. The light curve for the 28 stars observed by the satellite have been analyzed and the relevant periodogram presented. As a result we have found two binary, three Pulsating Be, three SPB, two Spotted and one ellipsoidal variables. Noteworthy, we have also identified one PMS δ Scuti candidate.

  17. 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.

  18. 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.

  19. The potential role of NGC 205 in generating Andromeda's vast thin corotating plane of satellite galaxies

    NASA Astrophysics Data System (ADS)

    Angus, Garry W.; Coppin, Paul; Gentile, Gianfranco; Diaferio, Antonaldo

    2016-11-01

    The Andromeda galaxy is observed to have a system of two large dwarf ellipticals and ˜13 smaller satellite galaxies that are currently corotating in a thin plane, in addition to 2 counter-rotating satellite galaxies. We explored the consistency of those observations with a scenario where the majority of the corotating satellite galaxies originated from a subhalo group, where NGC 205 was the host and the satellite galaxies occupied dark matter sub-subhaloes. We ran N-body simulations of a close encounter between NGC 205 and M31. In the simulations, NGC 205 was surrounded by massless particles to statistically sample the distribution of the sub-subhaloes expected in a subhalo that has a mass similar to NGC 205. We made Monte Carlo samplings and found that, using a set of reference parameters, the probability of producing a thinner distribution of sub-subhaloes than the observed NGC 205 + 15 smaller satellites (thus including the two counter-rotators, but excluding M32) increased from <10-8 for the initial distribution to ˜10-2 at pericentre. The probability of the simulated sub-subhaloes occupying the locations of the observed corotating satellites in the line-of-sight velocity versus projected on-sky distance plane is at most 2 × 10-3 for 11 out of 13 satellites. Increasing the mass of M31 and the extent of the initial distribution of sub-subhaloes gives a maximum probability of 4 × 10-3 for all 13 corotating satellites, but the probability of producing the thinness would drop to ˜10-3.

  20. 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).

  1. Exploring the Helium Core of the δ Scuti Star CoRoT 102749568 with Asteroseismology

    NASA Astrophysics Data System (ADS)

    Chen, Xinghao; Li, Yan; Lin, Guifang; Chen, Yanhui; Guo, Junjun

    2017-01-01

    Based on regularities in rotational splitting, we seek possible multiplets for the observed frequencies of CoRoT 102749568. There are 21 sets of multiplets identified, including four sets of multiplets with l = 1, nine sets of multiplets with l = 2, and eight sets of multiplets with l = 3. In particular, there are three complete triplets (f10, f12, f14), (f31, f34, f35), and (f41, f43, f44). The rotational period of CoRoT 102749568 is estimated to be {1.34}-0.05+0.04 days. When doing model fittings, three l = 1 modes (f12, f34, and f43) and the radial first overtone f13 are used. Our results shows that the three nonradial modes (f12, f34, and f43) are mixed modes, which mainly provide constraints on the helium core. The radial first overtone f13 mainly provides constraint on the stellar envelope. Hence the size of the helium core of CoRoT 102749568 is determined to be {M}{He} = 0.148 ± 0.003 M⊙ and {R}{He} = 0.0581 ± 0.0007 R⊙. The fundamental parameters of CoRoT 102749568 are determined to be M = 1.54 ± 0.03 M⊙, Z=0.006, {f}{ov}=0.004+/- 0.002, {log} g=3.696+/- 0.003, {T}{eff}=6886+/- 70 K, R = 2.916 ± 0.039 R⊙, and L = 17.12 ± 1.13 L⊙.

  2. 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.

  3. Interacting galaxies: corotating and counter-rotating systems with tidal tails

    NASA Astrophysics Data System (ADS)

    Mesa, Valeria; Duplancic, Fernanda; Alonso, Sol; Coldwell, Georgina; Lambas, Diego G.

    2014-02-01

    We analyse interacting galaxy pairs with evidence of tidal features in the Sloan Digital Sky Survey Data Release 7. The pairs were selected within z < 0.1 by requiring a projected separation rp < 50 h- 1 kpc and relative radial velocity ΔV < 500 km s-1. We complete spectroscopic pairs using galaxies with photometric redshifts considering ΔVphot < 6800 km s-1, taking into account the mean photometric redshift uncertainty. We classify by visual inspection pairs of spirals into corotating and counter-rotating systems. For a subsample of non-active galactic nucleus (non-AGN) galaxies, counter-rotating pairs have larger star formation rates and a higher fraction of young, star-forming galaxies. These effects are enhanced by restricting to rp < 12 h- 1 kpc. The distributions of C, Dn(4000) and (Mu - Mr) for AGN galaxies show that counter-rotating hosts have bluer colours and younger stellar population than the corotating galaxies although the relative fractions of Seyfert, LINER, Composite and Ambiguous AGN are similar. Also, counter-rotating hosts have more powerful AGN as revealed by enhanced Lum[O III] values. The number of corotating systems is approximately twice the number of counter-rotating pairs which could be owed to a more rapid evolution of counter-rotating systems, besides possible different initial conditions of these interacting pairs.

  4. Speckle Imaging of Kepler and CoRoT Exo-planet Transit Candidate Stars

    NASA Astrophysics Data System (ADS)

    Howell, Steve B.; Horch, Elliott; Sherry, William; Ciardi, David

    2010-08-01

    Kepler and CoRoT are complementary space missions dedicated to the detection of exoplanets. The primary science goal of CoRoT is to find Neptune-sized (>3 Earth radii) planets in intermediate orbits, while the prime science goal of Kepler is to find Earth-sized planets (<3 Earth radii) in year-long orbits. Both missions employ the photometric transit method and both spacecraft are performing well with nominal operation of the spacecraft, telescopes, electronics, and instruments. As with ground-based surveys, Kepler and CoRoT candidates need to be screened for background eclipsing binary stars which, when photometrically blended with the primary target, can mimic exo-planetary transits. The list of candidate transiting planets found by Kepler/CoRoT requires follow-up to ascertain probable or certain exo- planet detection. While Earth-sized (and Neptune-sized in long orbital periods) exo-planets can not currently (easily) be confirmed from the ground, many of the false positive eliminations steps can be performed by ground-based observations. Follow-up for Kepler exo-planet candidates is now aimed at Neptune-size and smaller planets in longer period orbits. This proposal aims to obtain high resolution speckle imaging to observe Kepler/CoRoT exo-planet transit candidates in order to eliminate the largest false positive contributor in any transit search - background eclipsing binary stars or faint companion stars.

  5. 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.

  6. 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

  7. On the width and shape of the corotation region for low-mass planets

    NASA Astrophysics Data System (ADS)

    Paardekooper, S.-J.; Papaloizou, J. C. B.

    2009-04-01

    We study the coorbital flow for embedded, low-mass planets. We provide a simple semi-analytic model for the corotation region, which is subsequently compared to high-resolution numerical simulations. The model is used to derive an expression for the half-width of the horseshoe region, xs, which in the limit of zero softening is given by xs/rp = 1.68(q/h)1/2, where q is the planet to central star mass ratio, h is the disc aspect ratio and rp is the orbital radius. This is in very good agreement with the same quantity measured from simulations. This result is used to show that horseshoe drag is about an order of magnitude larger than the linear corotation torque in the zero-softening limit. Thus, the horseshoe drag, the sign of which depends on the gradient of specific vorticity, is important for estimates of the total torque acting on the planet. We further show that phenomena, such as the Lindblad wakes, with a radial separation from corotation of approximately a pressure scaleheight H can affect xs, even though for low-mass planets xs << H. The effect is to distort streamlines and reduce xs through the action of a back pressure. This effect is reduced for smaller gravitational softening parameters and planets of higher mass, for which xs becomes comparable to H.

  8. A Model for Plasma Transport in a Corotation-Dominated Magnetosphere.

    NASA Astrophysics Data System (ADS)

    Pontius, Duane Henry, Jr.

    1988-06-01

    The gross structures of the magnetospheres of the outer planets are decided by processes quite different from those predominant in that of the earth. The terrestrial plasmapause, the boundary beyond which plasma motion is principally determined by magnetospheric interaction with the solar wind, is typically inside geosynchronous orbit. Within the plasmasphere, rotational effects are present, but gravity exceeds the centrifugal force of corotation. In contrast, the Jovian plasmasphere extends to a distance at least twenty times farther than synchronous orbit, affording a large region where rotational effects are expected to he clearly manifest (Brice and Ioannidis, 1970). The goal of this thesis is to develop an appropriate theoretical model for treating the problem of plasma transport in a corotation dominated plasmasphere. The model presented here is intended to describe the radial transport of relatively cold plasma having an azimuthally uniform distribution in a dipolar magnetic field. The approach is conceptually similar to that of the radial diffusion model in that small scale motions are examined to infer global consequences, but the physical understanding of those small scale motions is quite different. In particular, discrete flux tubes of small cross section are assumed to move over distances large compared to their widths. The present model also differs from the corotating convection model by introducing a mechanism whereby the conservation of flux tube content along flowlines is violated. However, it is quite possible that a global convection pattern co -exists with the motions described here, leading to longitudinal asymmetries in the plasma distribution.

  9. Modeling the propagation of solar energetic particles in corotating compression regions of solar wind

    NASA Astrophysics Data System (ADS)

    Kocharov, L.; Kovaltsov, G. A.; Torsti, J.; Anttila, A.; Sahla, T.

    2003-11-01

    We present the first modeling of solar energetic particle (SEP) events inside corotating compression regions. We consider gradual compressions in the interplanetary magnetic field brought on by interaction of the solar wind streams of different speed. The compression model is similar to that previously suggested for the acceleration of low-energy particles associated with corotating interaction regions (CIRs). In the framework of focused transport, we perform Monte Carlo simulations of the SEP propagation, adiabatic deceleration and reacceleration. A trap-like structure of the interplanetary magnetic field modifies the SEP intensity-time profiles, energy spectra, and anisotropy. Particle diffusion and adiabatic deceleration are typically reduced. For this reason, at a corotating vantage point the SEP event development after the intensity maximum is slower than would be expected based on the modeling in the standard, Archimedean spiral field. At the noncorotating spacecraft the magnetic tube convection past the observer becomes more important. The numerical model forms a basis on which to interpret SEP observations made by present and future spacecrafts at the longitude-dependent speed of solar wind. In particular, the modeling results are similar to the patterns observed with the ERNE particle telescope on board SOHO in August 1996. In the proton anisotropy data, we find a signature of the magnetic mirror associated with the CIR. A relation is established between the spectra observed at 1 AU and the SEP injection spectrum near the Sun.

  10. 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

  11. The evolution of barotropically unstable, high-Rossby number vortices in shear

    NASA Astrophysics Data System (ADS)

    Ryglicki, David R.

    The role of mesovortices in the eyewalls of sheared unstable, high-Rossby number vortices is investigated. A high-resolution numerical model is used to simulate dry vortices in an attempt to unite ideas from previous works. The simulations are used to investigate the dynamical, adiabatic interactions between potential vorticity (PV) mixing dynamics and shear forcings of barotropically unstable, high-Rossby number barotropic vortices. Previous work has investigated barotropic vortices in shear, while other previous work has studied barotropically unstable ring vortices. This work will combine those two avenues of research by shearing barotropically unstable barotropic ring vortices because ring vortices are more representative of tropical cyclones. Quantitative and qualitative analysis of the tilt and of the internal dynamics are presented. Using such as metrics as PV power spectra, PV palinstrophy, and a linear energy equation that incorporates the effects of the shear forcing, it is found that impact of the shear forcing on the initial breakdown of the ring is merely slight; however, the breakdown of the ring of high PV into smaller mesovortices---and the subsequent rearrangement of PV into a monopolar structure---is quite significant when considering the tilt evolution. As the vortex mixes, the storm weakens. This acts as a detriment to the ability of the vortex to keep itself upright and resistant to the shear forcing, as the penetration depth of each layer of the vortex decreases to below the scale height after mixing. In terms of the energetics, it is found that the barotropic energy conversion term is consistently the largest, which is expected. When sheared, the shear forcing acts to generally counteract the effects of mixing and reduce eddy kinetic energy. Additionally, it is found that the shear forcing induces a trochoidal oscillation at levels of highest background flow. The sensitivity of the results is investigated by comparing and contrasting two

  12. Projection operators for the Rossby and Poincare waves in a beta-plane approximation

    NASA Astrophysics Data System (ADS)

    Lebedkina, Anastasia; Ivan, Karpov; Sergej, Leble

    2013-04-01

    . The idea to use the polarization relations for the classification of waves originated in radio physics in the works of A. A. Novikov. In the theory of the electromagnetic field polarization relations is traditionally included in the analysis of wave phenomena. In the theory of acoustic-gravity waves, projection operators were introduced in a works of S. B. Leble. The object of study is a four-dimentional vector (components of the velocity, pressure and temperature). Based on these assumptions, we can construct the projection operators for superposition state on the linear basis, corresponding to the well-known type of waves. In this paper we consider procedure for construction of a projection operators for planetary Rossby and Poincare waves in the Earth's atmosphere in the approximation of the "beta-plane". In a result of work we constructed projection operators in this approximation for Poincare and Rossby waves. The tests for operators shown, that separation of the contribution of corresponding waves from source of the wave field is possible. Estimation accuracy of the operators and results of applying operators to the data TEC presented.

  13. Breaking Rossby Waves, Moisture Streamers, and the Southern Hemisphere Diagonal Convergence Zones

    NASA Astrophysics Data System (ADS)

    Panetta, R. L.; Ramotowski, M.

    2014-12-01

    A combination of satellite observations (principally GPCP) and ECMWF reanalyses were used to examine the major diagonal convergence zones in the Southern Hemisphere. Time-lag height anomalies composited on high rainfall events in sub-tropical and mid-latitude sections of the climatological zones showed nearly equivalent barotropic wave packets propagating into the regions from higher latitudes, in a manner easily interpretable in terms of the structure of low-pass-filtered pv gradients. To examine the moisture field with which the wave vertical motion field interacted in producing precipitation, animations were first constructed from daily fields of PV on the 330-theta surface superposed on total column water (TCW). The animations showed frequent events of anticyclonic breaking of mid-latitude Rossby waves, coincidental with the development of streamers of total column water (TCW) drawn out of the tropics, into the subtropics and mid-latitudes just downstream of parallel PV streamers in the breaking waves. Vertical cross sections through selected streamers showed locally high levels of moisture extending through most of the troposphere, with dynamically consistent vertical motion fields. Although major streamer events with NW-SE tilt could be seen in the animations, TCW streamers were in fact seen with many orientations and in many locations around the hemisphere. An objective method was developed to classify TCW streamers by their horizontal tilt. When applied to observations from the 20 year period 1991-2012, the method showed that TCW streamers with NW-SE tilt preferentially occurred in the three climatological diagonal convergence zones regions during austral summer, but only in the SPCZ and SACZ regions during austral winter.

  14. Solar wind dynamic pressure effect on planetary wave propagation and synoptic-scale Rossby wave breaking

    NASA Astrophysics Data System (ADS)

    Lu, Hua; Franzke, Christian; Martius, Olivia; Jarvis, Martin J.; Phillips, Tony

    2013-05-01

    We provide statistical evidence of the effect of the solar wind dynamic pressure (Psw) on the northern winter and spring circulations. We find that the vertical structure of the Northern Annular Mode (NAM), the zonal mean circulation, and Eliassen-Palm (EP)-flux anomalies show a dynamically consistent pattern of downward propagation over a period of ~45 days in response to positive Psw anomalies. When the solar irradiance is high, the signature of Psw is marked by a positive NAM anomaly descending from the stratosphere to the surface during winter. When the solar irradiance is low, the Psw signal has the opposite sign, occurs in spring, and is confined to the stratosphere. The negative Psw signal in the NAM under low solar irradiance conditions is primarily governed by enhanced vertical EP-flux divergence and a warmer polar region. The winter Psw signal under high solar irradiance conditions is associated with positive anomalies of the horizontal EP-flux divergence at 55°N-75°N and negative anomalies at 25°N-45°N, which corresponds to the positive NAM anomaly. The EP-flux divergence anomalies occur ~15 days ahead of the mean-flow changes. A significant equatorward shift of synoptic-scale Rossby wave breaking (RWB) near the tropopause is detected during January-March, corresponding to increased anticyclonic RWB and a decrease in cyclonic RWB. We suggest that the barotropic instability associated with asymmetric ozone in the upper stratosphere and the baroclinic instability associated with the polar vortex in the middle and lower stratosphere play a critical role for the winter signal and its downward propagation.

  15. Are Protoplanetary Disks Born with Vortices? Rossby Wave Instability Driven by Protostellar Infall

    NASA Astrophysics Data System (ADS)

    Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan

    2015-05-01

    We carry out two-fluid, two-dimensional global hydrodynamic simulations to test whether protostellar infall can trigger the Rossby wave instability (RWI) in protoplanetry disks. Our results show that infall can trigger the RWI and generate vortices near the outer edge of the mass landing on the disk (i.e., centrifugal radius). We find that the RWI is triggered under a variety of conditions, although the details depend on the disk parameters and the infall pattern. The common key feature of triggering the RWI is the steep radial gradient of the azimuthal velocity induced by the local increase in density at the outer edge of the infall region. Vortices form when the instability enters the nonlinear regime. In our standard model where self-gravity is neglected, vortices merge together to a single vortex within ˜20 local orbital times, and the merged vortex survives for the remaining duration of the calculation (>170 local orbital times). The vortex takes part in outward angular momentum transport, with a Reynolds stress of ≲10-2. Our two-fluid calculations show that vortices efficiently trap dust particles with stopping times of the order of the orbital time, locally enhancing the dust to gas ratio for particles of the appropriate size by a factor of ˜40 in our standard model. When self-gravity is considered, however, vortices tend to be impeded from merging and may eventually dissipate. We conclude it may well be that protoplanetary disks have favorable conditions for vortex formation during the protostellar infall phase, which might enhance early planetary core formation.

  16. 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.

  17. ARE PROTOPLANETARY DISKS BORN WITH VORTICES? ROSSBY WAVE INSTABILITY DRIVEN BY PROTOSTELLAR INFALL

    SciTech Connect

    Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan E-mail: lhartm@umich.edu

    2015-05-20

    We carry out two-fluid, two-dimensional global hydrodynamic simulations to test whether protostellar infall can trigger the Rossby wave instability (RWI) in protoplanetry disks. Our results show that infall can trigger the RWI and generate vortices near the outer edge of the mass landing on the disk (i.e., centrifugal radius). We find that the RWI is triggered under a variety of conditions, although the details depend on the disk parameters and the infall pattern. The common key feature of triggering the RWI is the steep radial gradient of the azimuthal velocity induced by the local increase in density at the outer edge of the infall region. Vortices form when the instability enters the nonlinear regime. In our standard model where self-gravity is neglected, vortices merge together to a single vortex within ∼20 local orbital times, and the merged vortex survives for the remaining duration of the calculation (>170 local orbital times). The vortex takes part in outward angular momentum transport, with a Reynolds stress of ≲10{sup −2}. Our two-fluid calculations show that vortices efficiently trap dust particles with stopping times of the order of the orbital time, locally enhancing the dust to gas ratio for particles of the appropriate size by a factor of ∼40 in our standard model. When self-gravity is considered, however, vortices tend to be impeded from merging and may eventually dissipate. We conclude it may well be that protoplanetary disks have favorable conditions for vortex formation during the protostellar infall phase, which might enhance early planetary core formation.

  18. 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.

  19. Excitation of the rossby waves due to the triple polarity reversal of the magnetic field

    NASA Astrophysics Data System (ADS)

    Pataraya, A. D.; Kaghashvili, E. Kh.; Pataraya, T. A.

    It is known that at the given latitude in the "Butterfly Diagram" of Maunder time interval between neighbouring wings is about 2 years (TI), and in this interval magnetic field changes its polarity. From the observed data it is known that in TI: (a) Magnetic field changes its sign once in both hemisphere of the Sun, or (b) There is the triple polarity reversal of the Magnetic field in the one of the hemisphere and single in the another. In another side, during the last two decades quasi bi-annual oscillations (QBAO) have been discovered both in variations of different characteristics of both solar features and geophysical phenomena. The quasi bi-annual oscillations were found out in variations of the solar radius (Sakurai 1981; Delarche et al., 1985), solar radioemission (Toman 1963) and variations of average monthly Wolf numbers (Toman 1963; Robin, 1984). In the present paper exitation of the linear waves is investigated in TI. Ideal MHD equations are used in β - plane considering that the toroidal component of the unperturbed velocity has a shear in the meridional direction. It is found that in case a constant shear there is single polarity reversal of the magnetic field in the both hemisphere. After considering QBAO in case of small amplitudes of QBAO the behavier of the magnetic field is as (a), and in case of large amplitudes as (b). It is found that at the polarity reversal there is strong excitation of the Rossby waves and they propagate from the middle latitudes to equator and poles. Energy flux is calculated.

  20. The dynamical impact of Rossby wave breaking upon UK PM10 concentration

    NASA Astrophysics Data System (ADS)

    Webber, Christopher P.; Dacre, Helen F.; Collins, William J.; Masato, Giacomo

    2017-01-01

    Coarse particulate matter (PM10) has long been understood to be hazardous to human health, with mortality rates increasing as a result of raised ground level concentrations. We explore the influence of synoptic-scale meteorology on daily mean observed PM10 concentration ([PM10]) using Rossby wave breaking (RWB). Meteorological reanalysis data for the winter months (DJF) between January 1999 and December 2008 and observed PM10 data for three urban background UK (Midland) sites were analysed. Three RWB diagnostics were used to identify RWB that had significant influence on UK Midland PM10. RWB events were classified according to whether the RWB was cyclonic or anticyclonic in its direction of breaking and whether the RWB event was influenced more by poleward or equatorial air masses. We find that there is a strong link between RWB events and UK [PM10]. Significant increases (p < 0.01) in UK [PM10] were seen 1 day following RWB occurring in spatially constrained northeast Atlantic-European regions. Analysis into episodic PM10 exceedance events shows increased probability of [PM10] exceedance associated with all RWB subsets. The greatest probability of exceeding the UK [PM10] threshold was associated with cyclonic RWB preceded by anticyclonic RWB forming an Ω block synoptic pattern. This mechanism suggests an easterly advection of European PM10 followed by prolonged stagnant conditions within the UK and led to an almost threefold increase in the probability of the UK Midlands exceeding a hazardous [PM10] threshold (0.383), when compared to days where no RWB was detected (0.129).

  1. 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

  2. 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.

  3. Seaglider Observations of Equatorial Ocean Rossby Wave Interactions With the Madden-Julian Oscillation During CINDY-DYNAMO

    NASA Astrophysics Data System (ADS)

    Webber, B. G.; Matthews, A. J.; Heywood, K. J.; Stevens, D. P.

    2012-12-01

    During the CINDY-DYNAMO field campaign in 2011-12, a Seaglider was deployed at 80°E in the Indian Ocean, and patrolled between 3° and 4°S over a period of three months. In addition, the periods when the Seaglider was travelling to and from the deployment location at 1.5°S represent two independent sections almost four months apart. The 3-4°S data have been optimally interpolated to generate unique and very high resolution data sets of temperature, salinity, chlorophyll and oxygen, along with derived geostrophic velocities in a region that has been under-observed to date. These observations reveal the importance of equatorial ocean Rossby waves in generating intraseasonal variability in the subsurface Indian Ocean, with temperature anomalies of around 0.5°C and salinity anomalies of 0.1 due to such waves. These anomalies extend with only slightly reduced magnitude into the deep ocean up to the maximum observed depth of 1000 m. The latitudinal structure of the temperature, salinity and density anomalies is generally very coherent, consistent with the structure of first meridional mode equatorial ocean Rossby waves. The chlorophyll and oxygen data from the Seaglider show how these waves have a substantial impact on biological activity at this location, with the peak productivity shifting vertically by up to 20 metres due to upwelling and downwelling. Linearised numerical ocean model simulations were conducted for the period around the Seaglider deployment period, to put the observations in context. These model simulations were forced by ERA-Interim winds that were filtered to remove the high-frequency variability while retaining that relating to the Madden-Julian Oscillation (MJO). Comparison between the model runs and Seaglider observations indicates that the MJO-related winds are directly responsible for a large portion of the observed ocean Rossby wave activity, although there is also a role for lower-frequency wind forcing. The model results also highlight

  4. 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

  5. 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

  6. 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.

  7. Overview of semi-sinusoidal stellar variability with the CoRoT satellite

    NASA Astrophysics Data System (ADS)

    De Medeiros, J. R.; Ferreira Lopes, C. E.; Leão, I. C.; Canto Martins, B. L.; Catelan, M.; Baglin, A.; Vieira, S.; Bravo, J. P.; Cortés, C.; de Freitas, D. B.; Janot-Pacheco, E.; Maciel, S. C.; Melo, C. H. F.; Osorio, Y.; Porto de Mello, G. F.; Valio, A.

    2013-07-01

    Context. To date, the CoRoT space mission has produced more than 124 471 light curves. Classifying these curves in terms of unambiguous variability behavior is mandatory for obtaining an unbiased statistical view on their controlling root-causes. Aims: The present study provides an overview of semi-sinusoidal light curves observed by the CoRoT exo-field CCDs. Methods: We selected a sample of 4206 light curves presenting well-defined semi-sinusoidal signatures. The variability periods were computed based on Lomb-Scargle periodograms, harmonic fits, and visual inspection. Results: Color-period diagrams for the present sample show the trend of an increase of the variability periods as long as the stars evolve. This evolutionary behavior is also noticed when comparing the period distribution in the Galactic center and anti-center directions. These aspects indicate a compatibility with stellar rotation, although more information is needed to confirm their root-causes. Considering this possibility, we identified a subset of three Sun-like candidates by their photometric period. Finally, the variability period versus color diagram behavior was found to be highly dependent on the reddening correction. 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.Table 2 is 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/555/A63

  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. Reassessing the radial-velocity evidence for planets around CoRoT-7

    NASA Astrophysics Data System (ADS)

    Pont, Frédéric; Aigrain, Suzanne; Zucker, Shay

    2011-03-01

    CoRoT-7 is an 11 th magnitude K-star whose light curve shows transits with a depth of 0.3 mmag and a period of 0.854 d, superimposed on variability at the 1 per cent level, due to the modulation of evolving active regions with the star's 23-d rotation period. In this paper, we revisit the published HARPS radial-velocity (RV) measurements of the object, which were previously used to estimate the companion mass, but have been the subject of ongoing debate. We build a realistic model of the star's activity during the HARPS observations, by fitting simultaneously the linewidth (as measured by the width of the cross-correlation function) and the line bisector, and use it to evaluate the contribution of activity to the RV variations. The data show clear evidence of errors above the level of the formal uncertainties, which are accounted for neither by activity nor by any plausible planet model and which increase rapidly with a decreasing signal-to-noise ratio (S/N) of the spectra. We cite evidence of similar systematics in mid-S/N spectra of other targets obtained with HARPS and other high-precision RV spectrographs, and discuss possible sources. Allowing for these, we re-evaluate the semi-amplitude of the CoRoT-7b signal, finding Kb= 1.6 ± 1.3 m s-1, a tentative detection with a much reduced significance (1.2σ) compared to previous estimates. We also argue that the combined presence of activity and additional errors precludes a meaningful search for additional low-mass companions, despite previous claims to the contrary. Taken at face value, our analysis points to a lower density for CoRoT-7b, the 1σ mass range spanning 1-4 M ⊕ and allowing for a wide range of bulk compositions. In particular, an ice-rich composition is compatible with the RV constraints. More generally, this study highlights the importance of a realistic treatment of both activity and uncertainties, particularly in the medium S/N regime, which applies to most small planet candidates from CoRoT and

  10. 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.

  11. Galactic Archaeology with CoRoT and APOGEE: Creating mock observations from a chemodynamical model

    NASA Astrophysics Data System (ADS)

    Anders, F.; Chiappini, C.; Rodrigues, T. S.; Piffl, T.; Mosser, B.; Miglio, A.; Montalbán, J.; Girardi, L.; Minchev, I.; Valentini, M.; Steinmetz, M.

    2016-09-01

    In a companion paper, we have presented the combined asteroseismic-spectroscopic dataset obtained from CoRoT light curves and APOGEE infra-red spectra for 606 solar-like oscillating red giants in two fields of the Galactic disc (CoRoGEE). We have measured chemical abundance patterns, distances, and ages of these field stars which are spread over a large radial range of the Milky Way's disc. Here we show how to simulate this dataset using a chemodynamical Galaxy model. We also demonstrate how the observation procedure influences the accuracy of our estimated ages.

  12. Variable Polarization from Co-Rotating Interaction Regions in Massive Star Winds

    NASA Astrophysics Data System (ADS)

    Ignace, Richard; St. Louis, Nicole; Tremblay, Patrick; Proulx-Giraldeau, Felix

    2017-01-01

    Co-rotating Interaction Regions (CIRs) are a well-known phenomenon in the solar wind, and is a favored culprit for certain cyclical behavior observed in the spectra of some massive stars. A prime example are the discrete absorption components (DACs) seen in the UV wind lines of many O stars. Here we report on modeling for the variable continuum polarization that could arise from the presence of CIR structures. Considerations are limited to optically thin scattering. Using a core-halo approach for winds that are thick to electron scattering, an application to observed variable polarization of WR6 (EZ CMa; HD 50896) is presented.

  13. LONG-TERM VARIATION IN THE SUN’S ACTIVITY CAUSED BY MAGNETIC ROSSBY WAVES IN THE TACHOCLINE

    SciTech Connect

    Zaqarashvili, Teimuraz V.; Oliver, Ramon; Ballester, Jose Luis; Hanslmeier, Arnold; Carbonell, Marc; Gachechiladze, Tamar; Usoskin, Ilya G.

    2015-06-01

    Long-term records of sunspot number and concentrations of cosmogenic radionuclides (10Be and 14C) on the Earth reveal the variation of the Sun's magnetic activity over hundreds and thousands of years. We identify several clear periods in sunspot, 10Be, and 14C data as 1000, 500, 350, 200, and 100 years. We found that the periods of the first five spherical harmonics of the slow magnetic Rossby mode in the presence of a steady toroidal magnetic field of 1200–1300 G in the lower tachocline are in perfect agreement with the timescales of observed variations. The steady toroidal magnetic field can be generated in the lower tachocline either due to the steady dynamo magnetic field for low magnetic diffusivity or due to the action of the latitudinal differential rotation on the weak poloidal primordial magnetic field, which penetrates from the radiative interior. The slow magnetic Rossby waves lead to variations of the steady toroidal magnetic field in the lower tachocline, which modulate the dynamo magnetic field and consequently the solar cycle strength. This result constitutes a key point for long-term prediction of the cycle strength. According to our model, the next deep minimum in solar activity is expected during the first half of this century.

  14. Transiting exoplanets from the CoRoT space mission. XI. CoRoT-8b: a hot and dense sub-Saturn around a K1 dwarf

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

    Aims: We report the discovery of CoRoT-8b, a dense small Saturn-class exoplanet that orbits a K1 dwarf in 6.2 days, and we derive its orbital parameters, mass, and radius. Methods: We analyzed two complementary data sets: the photometric transit curve of CoRoT-8b as measured by CoRoT and the radial velocity curve of CoRoT-8 as measured by the HARPS spectrometer. Results: We find that CoRoT-8b is on a circular orbit with a semi-major axis of 0.063 ± 0.001 AU. It has a radius of 0.57 ± 0.02 RJ, a mass of 0.22 ± 0.03 MJ, and therefore a mean density of 1.6 ± 0.1 g cm-3. Conclusions: With 67% of the size of Saturn and 72% of its mass, CoRoT-8b has a density comparable to that of Neptune (1.76 g cm-3). We estimate its content in heavy elements to be 47-63 {M}_⊕, and the mass of its hydrogen-helium envelope to be 7-23 {M}_⊕. At 0.063 AU, the thermal loss of hydrogen of CoRoT-8b should be no more than 0.1% over an assumed integrated lifetime of 3 Ga. Observations made with SOPHIE spectrograph at Observatoire de Haute Provence, France (PNP.07B.MOUT), and the HARPS spectrograph at ESO La Silla Observatory (081.C-0388 and 083.C-0186). 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.Both data sets are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/520/A66

  15. 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.

  16. Corotating and transient structures of IMF at Venus and Earth orbits

    NASA Technical Reports Server (NTRS)

    Marubashi, K.

    1995-01-01

    Magnetometer data obtained from the Pioneer Venus orbiter (PVO) provide a unique data base for studying interplanetary magnetic field (IMF) structures at 0.7 AU. Comparison of the same structure observed at 0.7 and 1 AU provides information about the effects of stream interactions between these two distances. Besides, the PVO observations provide solar wind conditions at various longitude separations from the Sun-Earth line, because the orbital motion of Venus is about 0.6 deg/day faster than that of Earth. Thus, it is possible to examine the effects of time variations in the coronal conditions on the solar wind conditions by comparing corotating structures observed at Earth and those from the PVO at different longitude separations. Some results obtained so far are as follows. We have found several transient structures observed at both 0.7 and 1 AU, when the Sun, Venus, and Earth are closely aligned. Each event exhibits magnetic field variations very similar to each other between Venus and Earth, implying that the effects of stream interactions are small. The IMF sector boundaries were compared between the Venus and Earth orbits as typical examples of corotating structures. We have found both well-correlated and poorly-correlated structures depending on the longitude separation between the Earth and Venus, and on the persistence of the sector structures.

  17. 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.

  18. 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.

  19. Semi-empirical seismic relations of A-F stars from COROT and Kepler legacy data

    NASA Astrophysics Data System (ADS)

    Moya, A.; Suárez, J. C.; García Hernández, A.; Mendoza, M. A.

    2017-10-01

    Asteroseismology is witnessing a revolution, thanks to high-precise asteroseismic space data (MOST, COROT, Kepler, BRITE) and their large ground-based follow-up programs. Those instruments have provided an unprecedented large amount of information, which allows us to scrutinize its statistical properties in the quest for hidden relations among pulsational and/or physical observables. This approach might be particularly useful for stars whose pulsation content is difficult to interpret. This is the case of intermediate-mass classical pulsating stars (i.e. γ Dor, δ Scuti, hybrids) for which current theories do not properly predict the observed oscillation spectra. Here, we establish a first step in finding such hidden relations from data mining techniques for these stars. We searched for those hidden relations in a sample of δ Scuti and hybrid stars observed by COROT and Kepler (74 and 153, respectively). No significant correlations between pairs of observables were found. However, two statistically significant correlations emerged from multivariable correlations in the observed seismic data, which describe the total number of observed frequencies and the largest one, respectively. Moreover, three different sets of stars were found to cluster according to their frequency density distribution. Such sets are in apparent agreement with the asteroseismic properties commonly accepted for A-F pulsating stars.

  20. Ulysses high-latitude observations of ions accelerated by co-rotating interaction regions

    NASA Technical Reports Server (NTRS)

    Sanderson, T. R.; Marsden, R. G.; Wenzel, K.-P.; Balogh, A.; Forsyth, R. J.; Goldstein, B. E.

    1994-01-01

    We present observations of energetic ions (E approximately 1 MeV) from the Ulysses spacecraft during its first pass from the ecliptic plane to the southern high-latitude regions of the heliosphere. At latitudes less than approximately 13 deg S Ulysses was completely immersed in the heliomagnetic streamer belt, and observed a approximately 1 MeV proton intensity which showed little evidence of a periodic structure. Between approximately 13 deg S and approximately 29 deg S Ulysses observed one dominant recurrent co-rotating interaction region, its reverse shocks being mainly responsible for accelerating the approximately 1 MeV protons. At approximately 29 deg S the spacecraft left this region and entered the solar wind flow from the polar coronal hole. From approximately 29 deg up to approximately 45 deg S, reverse shocks from this and other interaction regions were still being observed. Accelerated energetic ions, with proton-to-alpha ratio signatures consistent with having been accelerated by the reverse shocks of these co-rotating interacting regions, were still being observed up to latitudes of approximately 50 deg S.

  1. Synergies of CoRoT asteroseismology and APOGEE spectroscopy -- Applications to Galactic Archaeology

    NASA Astrophysics Data System (ADS)

    Anders, Friedrich; Chiappini, Cristina; Silva Rodrigues, Thaíse; Miglio, Andrea; Montalbàn, Josefina; Mosser, Benoit; Girardi, Leo; Valentini, Marica; Steinmetz, Matthias

    2015-08-01

    We present the first coherent dataset of 678 solar-like oscillating CoRoT red-giant stars located in two fields of the Galactic disc which have been followed up spectroscopically by the Apache Point Observatory Galactic Evolution Experiment (APOGEE).For the first time in a homogeneous analysis, ages and chemical abundance patterns of field stars have been measured over a largeradial range of the Milky Way's disc (4.5 kpc corotation.We also highlight some possibilities to use the present sample to constrain stellar models (thermo-haline mixing, determining evolutionary stages from spectroscopy alone).

  2. 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.

  3. Corotating and transient structures of IMF at Venus and Earth orbits

    NASA Technical Reports Server (NTRS)

    Marubashi, K.

    1995-01-01

    Magnetometer data obtained from the Pioneer Venus orbiter (PVO) provide a unique data base for studying interplanetary magnetic field (IMF) structures at 0.7 AU. Comparison of the same structure observed at 0.7 and 1 AU provides information about the effects of stream interactions between these two distances. Besides, the PVO observations provide solar wind conditions at various longitude separations from the Sun-Earth line, because the orbital motion of Venus is about 0.6 deg/day faster than that of Earth. Thus, it is possible to examine the effects of time variations in the coronal conditions on the solar wind conditions by comparing corotating structures observed at Earth and those from the PVO at different longitude separations. Some results obtained so far are as follows. We have found several transient structures observed at both 0.7 and 1 AU, when the Sun, Venus, and Earth are closely aligned. Each event exhibits magnetic field variations very similar to each other between Venus and Earth, implying that the effects of stream interactions are small. The IMF sector boundaries were compared between the Venus and Earth orbits as typical examples of corotating structures. We have found both well-correlated and poorly-correlated structures depending on the longitude separation between the Earth and Venus, and on the persistence of the sector structures.

  4. The characteristics of the corotating aurora observed at Poker Flat, Alaska

    NASA Astrophysics Data System (ADS)

    Toyoshima, S.; Fukunishi, H.; Yoshida, N.; Kubota, M.; Murayama, Y.

    2002-12-01

    As part of the CRL-UAF cooperative middle atmosphere project, monochromatic imaging observations of aurora and airglow have been carried out at Poker Flat (65.1N, 212.6E; 65.6 MLAT: MLT = UT-13 hours) since October 2000. Monochromatic images are obtained every 5 minutes using two all-sky imagers at 10 emission lines, i.e., HŸA (486.1 nm), OI (557.7 nm), N2+ (427.8 nm), background (572 nm), Na (589 nm), HŸA background (481 nm), OI (630.0 nm), OI (844.6 nm), OI (777.4 nm), and OI (630 nm). From these data, the new type of aurora which keeps its patch structure at some fixed location in the field of view was found in the magnetic evening sector by Kubota and Nagatsuma [2001]. These characteristics suggest that this type of aurora was corotating with the Earth. We have investigated the characteristics of such 'corotating aurora' in detail using 29 events identified in the period from October 2000 to April 2002. While imaging observation covers from 14 to 07 MLT, this type of aurora is observed only in the dusk to midnight sector (14 - 03 MLT). The aurora occurs on geomagnetic quiet conditions (Kp=0 - 3+) after the decay of substorm activity. The occurrence of this type of aurora are identified at emission lines, OI 557.7 nm, N2+ 427.8 and OI 844.6 nm, but not at OI 630.0 nm and HŸA 486.1 nm. This feature suggests that this type of aurora is excited by precipitating hard electrons. Precipitating electron and ion data obtained by DMSP/SSJ showed that the precipitating electrons with energies of few keV are the source of this aurora, and that precipitating ions are absent. Using simultaneous IMAGE/EUV (Extreme Ultraviolet Imager) data, we have examined the relationship between the corotating aurora mapped to the equatorial plane and the structure of the plasmasphere in three events observed on February 23, 24 and March 1, 2001. In these events it seems the plasmapause was unclear and the corotating aurora was mapped to the low plasma density region of ~102 /cm3. We

  5. Modelling the Influence of Tropically-Excited Poleward Propagating Rossby Waves and their influence on recent Arctic Climate Change.

    NASA Astrophysics Data System (ADS)

    McCrystall, M.; Hosking, J. S.; Maycock, A.; Pyle, J. A.

    2016-12-01

    Identifying the key drivers of Arctic climate is essential for understanding the recent changes in local climate and the mechanisms for these changes. Remote sea-surface temperatures (SSTs) have been identified by Ding et al. (2014) as a driver of these recent changes by inducing surface and mid-tropospheric warming and increase in 200 hPa geopotential heights (Z200), particularly over northern Canada and Greenland. This work further investigates the robustness of the Tropical-Arctic teleconnection by assessing the role of tropical SSTs in exciting planetary scale Rossby waves, and determining their effect on Arctic climate. We analyse a series of sensitivity experiments, using the Met Office HadGEM3 atmospheric model, forced by observed changes in SSTs between the periods 1979-1988 and 2003-2012 imposed for; [i] the entire tropics, [ii] the tropical Pacific Ocean and [iii] the tropical Atlantic Ocean. The spatial patterns of Z200 anomalies in the experiments are quantitatively compared to the 27-year Z200 trends from ERA-Interim reanalysis data and the model results of Ding et al. (2014). In contrast to their results, we found negative Z200 anomalies over northern Canada and Greenland in boreal winter in response to recent changes in tropical SSTs. We capture, however, an increase in Z200 of around 20 m over Scandinavia and the Aleutian Islands. To understand the direct influence of the tropical SST forcing on high latitudes, we analyse 3D wave activity flux anomalies, based on Plumb (1985). There is large variability in northern hemisphere wave flux anomalies but we do identify a Rossby wave train from the tropical Atlantic projecting onto the anomalous Z200 over Scandinavia. The results suggest changes in tropical SSTs can affect regional Arctic climate through their effect on poleward propagating Rossby waves, however from these experiments, it appears that this process has not contributed to the recent observed Z200 trends over northern Canada and Greenland

  6. 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

  7. An evaluation of the classical and extended Rossby wave theories in explaining spectral estimates of the first few baroclinic modes in the South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Maharaj, Angela M.; Cipollini, Paolo; Holbrook, Neil J.; Killworth, Peter D.; Blundell, Jeffrey R.

    2007-06-01

    Previous literature has suggested that multiple peaks in sea level anomalies (SLA) detected by two-dimensional Fourier Transform (2D-FT) analysis are spectral components of multiple propagating signals, which may correspond to different baroclinic Rossby wave modes. We test this hypothesis in the South Pacific Ocean by applying a 2D-FT analysis to the long Rossby wave signal determined from filtered TOPEX/Poseidon and European Remote Sensing-1/2 satellite altimeter derived SLA. The first four baroclinic mode dispersion curves for the classical linear wave theory and the Killworth and Blundell extended theory are used to determine the spectral signature and energy contributions of each mode. South of 17°S, the first two extended theory modes explain up to 60% more of the variance in the observed power spectral energy than their classical linear theory counterparts. We find that Rossby wave modes 2 3 contribute to the total Rossby wave energy in the SLA data. The second mode contributes significantly over most of the basin. The third mode is also evident in some localized regions of the South Pacific but may be ignored at the large scale. Examination of a selection of case study sites suggests that bathymetric effects may dominate at longer wavelengths or permit higher order mode solutions, but mean flow tends to be the more influential factor in the extended theory. We discuss the regional variations in frequency and wave number characteristics of the extended theory modes across the South Pacific basin.

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

    DTIC Science & Technology

    2009-01-01

    mission developed by NASA and the Space Agency of Argentina ( Comision Nacional de Actividades Espaciales, CONAE), which is planned for launch in May...notably ESA’s Soil Moisture and Ocean Salinity (SMOS) and joint U.S. and Argentina Aquarius missions, will open a new era in Rossby wave studies using

  9. Free and Forced Rossby Waves in the Western South China Sea Inferred from Jason-1 Satellite Altimetry Data.

    PubMed

    Wu, Xiangyu; Xie, Qiang; He, Zhigang; Wang, Dongxiao

    2008-06-01

    Data from a subsurface mooring deployed in the western South China Sea shows clear intra-seasonal oscillations (ISO) at the period of 40~70 days. Analysis of remotelysensed sea surface height (SSH) anomalies in the same area indicates that these ISO signals propagate both eastward and westward. Time-longitude diagrams of ISO signals in SSH anomalies and wind-stress curl indicate that the eastward propagating SSH anomalies is forced by wind-stress curl. This is also confirmed by lag correlation between SSH anomalies and the wind-stress-curl index (wind stress curl averaged over 109.5ºE -115ºE and 12ºN -13.5ºN). Lag correlation of SSH anomaly suggests that the westward propagating signals are free Rossby waves.

  10. 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.

  11. 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.

  12. Free and Forced Rossby Waves in the Western South China Sea Inferred from Jason-1 Satellite Altimetry Data

    PubMed Central

    Wu, Xiangyu; Xie, Qiang; He, Zhigang; Wang, Dongxiao

    2008-01-01

    Data from a subsurface mooring deployed in the western South China Sea shows clear intra-seasonal oscillations (ISO) at the period of 40∼70 days. Analysis of remotely-sensed sea surface height (SSH) anomalies in the same area indicates that these ISO signals propagate both eastward and westward. Time-longitude diagrams of ISO signals in SSH anomalies and wind-stress curl indicate that the eastward propagating SSH anomalies is forced by wind-stress curl. This is also confirmed by lag correlation between SSH anomalies and the wind-stress-curl index (wind stress curl averaged over 109.5°E -115°E and 12°N -13.5°N). Lag correlation of SSH anomaly suggests that the westward propagating signals are free Rossby waves. PMID:27879897

  13. 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).

  14. 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.

    2016-12-01

    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.

  15. Simulated austral winter response of the Hadley circulation and stationary Rossby wave propagation to a warming climate

    NASA Astrophysics Data System (ADS)

    Freitas, Ana C. V.; Frederiksen, Jorgen S.; O'Kane, Terence J.; Ambrizzi, Tércio

    2016-09-01

    Ensemble simulations, using both coupled ocean-atmosphere (AOGCM) and atmosphere only (AGCM) general circulation models, are employed to examine the austral winter response of the Hadley circulation (HC) and stationary Rossby wave propagation (SRW) to a warming climate. Changes in the strength and width of the HC are firstly examined in a set of runs with idealized sea surface temperature (SST) perturbations as boundary conditions in the AGCM. Strong and weak SST gradient experiments (SG and WG, respectively) simulate changes in the HC intensity, whereas narrow (5°S-5°N) and wide (30°S-30°N) SST warming experiments simulate changes in the HC width. To examine the combined impact of changes in the strength and width of the HC upon SRW propagation two AOGCM simulations using different scenarios of increasing carbon dioxide (CO2) concentrations are employed. We show that, in contrast to a wide SST warming, the atmospheric simulations with a narrow SST warming produce stronger and very zonally extended Rossby wave sources, leading to stronger and eastward shifted troughs and ridges. Simulations with SST anomalies, either in narrow or wide latitude bands only modify the intensity of the troughs and ridges. SST anomalies outside the narrow latitude band of 5°S-5°N do not significantly affect the spatial pattern of SRW propagation. AOGCM simulations with 1 %/year increasing CO2 concentrations or 4 times preindustrial CO2 levels reveal very similar SRW responses to the atmospheric only simulations with anomalously wider SST warming. Our results suggest that in a warmer climate, the changes in the strength and width of the HC act in concert to significantly alter SRW sources and propagation characteristics.

  16. Rossby wave breaking and Lagrangian structures inside the Antarctic stratospheric polar vortex during Vorcore and Concordiasi campaigns

    NASA Astrophysics Data System (ADS)

    de la Camara, Alvaro; Mechoso, Carlos R.; Mancho, Ana M.; Serrano, Encarna; Ide, Kayo

    2013-04-01

    The trajectories in the lower stratosphere of isopycnic balloons released from Antarctica by international field campaigns during the southern springs of 2005 and 2010 showed events of latitudinal transport inside the stratospheric polar vortex, both away and towards the poleward flank of the polar night jet. The present work applies trajectory-based diagnostic techniques to examine mechanisms at work during such events. Reverse domain filling calculations of potential vorticity (PV) fields from ECMWF ERA-Interim data set during the events show irreversible filamentation of the PV fields in the inner side of the polar night jet, which is a signature of planetary (Rossby) wave breaking. Balloons motions during the events are fairly consistent with the PV filaments. Events of both large (~15° of arch length) and small (~5° of arch length) balloon displacements from the vortex edge are associated to deep and shallow penetration into the core of the elongated PV contours. The function M is applied to study the configuration of Lagrangian coherent structures during the events. A close association is found between hyperbolic points and breaking waves inside the vortex. The geometric configuration of the invariant manifolds associated with the hyperbolic points helps to understand the apparent chaotic behavior of balloons motions, and to identify and analyze balloon transport events not captured by the Reverse Domain Filling calculations. The Antarctic polar vortex edge is an effective barrier to air parcel crossings. Rossby wave breaking inside the vortex, however, can contribute to tracer mixing inside the vortex and to occasional air crossings of the edge.

  17. Simulated austral winter response of the Hadley circulation and stationary Rossby wave propagation to a warming climate

    NASA Astrophysics Data System (ADS)

    Freitas, Ana C. V.; Frederiksen, Jorgen S.; O'Kane, Terence J.; Ambrizzi, Tércio

    2017-07-01

    Ensemble simulations, using both coupled ocean-atmosphere (AOGCM) and atmosphere only (AGCM) general circulation models, are employed to examine the austral winter response of the Hadley circulation (HC) and stationary Rossby wave propagation (SRW) to a warming climate. Changes in the strength and width of the HC are firstly examined in a set of runs with idealized sea surface temperature (SST) perturbations as boundary conditions in the AGCM. Strong and weak SST gradient experiments (SG and WG, respectively) simulate changes in the HC intensity, whereas narrow (5°S-5°N) and wide (30°S-30°N) SST warming experiments simulate changes in the HC width. To examine the combined impact of changes in the strength and width of the HC upon SRW propagation two AOGCM simulations using different scenarios of increasing carbon dioxide (CO2) concentrations are employed. We show that, in contrast to a wide SST warming, the atmospheric simulations with a narrow SST warming produce stronger and very zonally extended Rossby wave sources, leading to stronger and eastward shifted troughs and ridges. Simulations with SST anomalies, either in narrow or wide latitude bands only modify the intensity of the troughs and ridges. SST anomalies outside the narrow latitude band of 5°S-5°N do not significantly affect the spatial pattern of SRW propagation. AOGCM simulations with 1 %/year increasing CO2 concentrations or 4 times preindustrial CO2 levels reveal very similar SRW responses to the atmospheric only simulations with anomalously wider SST warming. Our results suggest that in a warmer climate, the changes in the strength and width of the HC act in concert to significantly alter SRW sources and propagation characteristics.

  18. 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

  19. HD 174884: a strongly eccentric, short-period early-type binary system discovered by CoRoT

    NASA Astrophysics Data System (ADS)

    Maceroni, C.; Montalbán, J.; Michel, E.; Harmanec, P.; Prsa, A.; Briquet, M.; Niemczura, E.; Morel, T.; Ladjal, D.; Auvergne, M.; Baglin, A.; Baudin, F.; Catala, C.; Samadi, R.; Aerts, C.

    2009-12-01

    Accurate photometric CoRoT space observations of a secondary seismological target, HD 174884, led to the discovery that this star is an astrophysically important double-lined eclipsing spectroscopic binary in an eccentric orbit (e˜0.3), unusual for its short 3.65705° orbital period. The high eccentricity, coupled with the orientation of the binary orbit in space, explains the very unusual observed light curve with strongly unequal primary and secondary eclipses having the depth ratio of 1-to-100 in the CoRoT “seismo” passband. Without the high accuracy of the CoRoT photometry, the secondary eclipse, 1.5 mmag deep, would have gone unnoticed. A spectroscopic follow-up program provided 45 high dispersion spectra. The analysis of the CoRoT light curve was performed with an adapted version of PHOEBE that supports CoRoT passbands. The final solution was obtained by a simultaneous fitting of the light and the radial velocity curves. Individual star spectra were obtained by spectrum disentangling. The uncertainties of the fit were achieved by bootstrap resampling and the solution uniqueness was tested by heuristic scanning. The results provide a consistent picture of the system composed of two late B stars. The Fourier analysis of the light curve fit residuals yields two components, with orbital frequency multiples and an amplitude of ~0.1 mmag, which are tentatively interpreted as tidally induced pulsations. An extensive comparison with theoretical models is carried out by means of the Levenberg-Marquardt minimization technique, and the discrepancy between the models and the derived parameters is discussed. The best fitting models yield a young system age of 125 million years which is consistent with the eccentric orbit and synchronous component rotation at periastron. Based on photometry collected by the CoRoT space mission and spectroscopy obtained with the CORALIE spectrograph attached to the 1.2 m Euler telescope at ESO, La Silla, Chile. The CoRoT space mission

  20. Influence of the Earth s Corotation Field on the Atmospheric Electricity: Latitudinal Variation and Response to the Solar Activity

    NASA Astrophysics Data System (ADS)

    Dumin, Y.

    Influence of the magnetospheric convection field on the atmospheric electricity is widely studied, both theoretically and experimentally, from the early 1970s. On the other hand, a considerably less attention was paid to the effects of plasmaspheric corotation field, since it was usually believed that the electric field of corotation of the solid Earth is fitted smoothly to the corotation field of plasmasphere, so that no potential difference is formed between them in the lower atmosphere. A conjecture on the important role of corotation field in the global atmospheric-electric circuit was done a few years ago in [P.A. Bespalov, Yu.V. Chugunov, J. Atmos. Terr. Phys., 1996, v.58, p.601] and several subsequent works. Unfortunately, because of using an oversimplified model of plasmasphere (in the form of a spherically-symmetric envelope with isotropic conductivity and rigid-body rotation), no reliable numerical estimates were derived, and no comparison with experimental distributions of the atmospheric electric field could be conducted. The main aim of the present report is to study the corotation effects in the framework of a considerably more realistic analytical model, where conductivity of the plasmasphere is strongly anisotropic, and the magnetic field lines are substantially distorted (stretched to "infinity") in the polar regions. Escape of polarization electric charges along the distorted field lines results in appreciable decrease (by 10-15 V/m) in the average atmospheric electric field at high latitudes. Such phenomenon was experimentally discovered as early as the International Geophysical Year (1957-1958) but was not quantitatively explained by now. Yet another interesting effect following from our model is changing the high-latitude electric field due to variations in the degree of distortion of the magnetic field lines at different levels of the solar activity. These transient changes in the atmospheric electricity should be symmetric about the noon

  1. Photospheric activity, rotation, and star-planet interaction of the planet-hosting star CoRoT-6

    NASA Astrophysics Data System (ADS)

    Lanza, A. F.; Bonomo, A. S.; Pagano, I.; Leto, G.; Messina, S.; Cutispoto, G.; Moutou, C.; Aigrain, S.; Alonso, R.; Barge, P.; Deleuil, M.; Fridlund, M.; Silva-Valio, A.; Auvergne, M.; Baglin, A.; Collier Cameron, A.

    2011-01-01

    Context. The CoRoT satellite has recently discovered a hot Jupiter that transits across the disc of a F9 main-sequence star called CoRoT-6 with a period of 8.886 days. Aims: We model the photospheric activity of the star and use the maps of the active regions to study stellar differential rotation and the star-planet interaction. Methods: We apply a maximum entropy spot model to fit the optical modulation as observed by CoRoT during a uninterrupted interval of ~ 140 days. Photospheric active regions are assumed to consist of spots and faculae in a fixed proportion with solar-like contrasts. Results: Individual active regions have lifetimes up to 30-40 days. Most of them form and decay within five active longitudes whose different migration rates are attributed to the stellar differential rotation for which a lower limit of ΔΩ/Ω = 0.12 ± 0.02 is obtained. Several active regions show a maximum of activity at a longitude lagging the subplanetary point by ~ 200° with the probability of a chance occurrence being smaller than 1 percent. Conclusions: Our spot modelling indicates that the photospheric activity of CoRoT-6 could be partially modulated by some kind of star-planet magnetic interaction, while an interaction related to tides is highly unlikely because of the weakness of the tidal force. Based on observations obtained with CoRoT, a space project operated by the French Space Agency, CNES, with partecipation of the Science Programme of ESA, ESTEC/RSSD, Austria, Belgium, Brazil, Germany, and Spain.

  2. Comparative clustering analysis of variable stars in the Hipparcos, OGLE Large Magellanic Cloud, and CoRoT exoplanet databases

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

    Context: Discovery of new variability classes in large surveys using multivariate statistics techniques such as clustering, relies heavily on the correct understanding of the distribution of known classes as point processes in parameter space. Aims: Our objective is to analyze the correspondence between the classical stellar variability types and the clusters found in the distribution of light curve parameters and colour indices of stars in the CoRoT exoplanet sample. The final aim is to help in the identification on new types of variability by first identifying the well known variables in the CoRoT sample. Methods: We apply unsupervised classification algorithms to identify clusters of variable stars from modes of the probability density distribution. We use reference variability databases (Hipparcos and OGLE) as a framework to calibrate the clustering methodology. Furthermore, we use the results from supervised classification methods to interpret the resulting clusters. Results: We interpret the clusters in the Hipparcos and OGLE LMC databases in terms of large-amplitude radial pulsators in the classical instability strip and of various types of eclipsing binaries. The Hipparcos data also provide clear distributions for low-amplitude nonradial pulsators. We show that the preselection of targets for the CoRoT exoplanet programme results in a completely different probability density landscape than the OGLE data, the interpretation of which involves mainly classes of low-amplitude variability in main-sequence stars. Our findings will be incorporated to improve the supervised classification used in the CoRoT catalogue production, once the existence of new classes or subtypes will be confirmed from complementary spectroscopic observations. 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.

  3. Regular Motions of Resonant Asteroids

    NASA Astrophysics Data System (ADS)

    Ferraz-Mello, S.

    1990-11-01

    RESUMEN. Se revisan resultados analiticos relativos a soluciones regulares del problema asteroidal eliptico promediados en la vecindad de una resonancia con jupiten Mencionamos Ia ley de estructura para libradores de alta excentricidad, la estabilidad de los centros de liberaci6n, las perturbaciones forzadas por la excentricidad de jupiter y las 6rbitas de corotaci6n. ABSTRAC This paper reviews analytical results concerning the regular solutions of the elliptic asteroidal problem averaged in the neighbourhood of a resonance with jupiter. We mention the law of structure for high-eccentricity librators, the stability of the libration centers, the perturbations forced by the eccentricity ofjupiter and the corotation orbits. Key words: ASThROIDS

  4. VizieR Online Data Catalog: Supervised classification of CoRoT variables (Debosscher+, 2009)

    NASA Astrophysics Data System (ADS)

    Debosscher, J.; Sarro, L. M.; Lopez, M.; Deleuil, M.; Aerts, C.; Auvergne, M.; Baglin, A.; Baudin, F.; Chadid, M.; Charpinet, S.; Cuypers, J.; De Ridder, J.; Garrido, R.; Hubert, A. M.; Janot-Pacheco, E.; Jorda, L.; Kaiser, A.; Kallinger, T.; Kollath, Z.; Maceroni, C.; Mathias, P.; Michel, E.; Moutou, C.; Neiner, C.; Ollivier, M.; Samadi, R.; Solano, E.; Surace, C.; Vandenbussche, B.; Weiss, W. W.

    2009-10-01

    Light curve parameters and classification results are presented for all the objects measured in the first four CoRoT observing runs: IRa01, SRc01, LRc01, and LRa01. The information presented here should allow scientists to make candidate lists of their objects of study and to obtain some basic light curve information. We recall that we did not perform detailed light curve modelling, only a basic one, sufficient for producing variability class memberships for each target. We refer to the paper for a detailed description of the light curve parameters, and the classification results. It is strongly advised to read the paper prior to using the results presented here. (4 data files).

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

    NASA Astrophysics Data System (ADS)

    Soong, C. Y.; Yan, W. M.

    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.

  6. Stellar rotation at young ages: new results from Corot's monitoring NGC 2264

    NASA Astrophysics Data System (ADS)

    Favata, F.; Micela, G.; Alencar, S.; Aigrain, S.; Zwintz, K.

    2010-11-01

    Stellar rotation at young ages: new results from Corot's Angular momentum is one of the driving forces in the early evolution of stars. Issues such as the coupling between the star and the accretion disk (the so-called disk regulation paradigm), are traced by the evolution of rotational momentum, but affect the star-forming process as a whole. One of the features observed in star-forming regions (e.g. ONC and NGC 2264) of age between 1 and few Myr, for masses above 0.25 solar masses, is a bimodality of the rotational period distribution, with a peak around 1 day and the other at around 4 to 7 days. This bimodality has been interpreted as the smoking gun of the disk-locking mechanism (with the fast rotators having lost their disk and the slow ones still being regulated by their disks).

  7. Looking for planetary candidates in the CoRoT Long Run LRc10

    NASA Astrophysics Data System (ADS)

    Zannoni, A.; Borsa, F.; Poretti, E.; Lodato, G.; Rainer, M.; Frustagli, G.

    We analysed the public data of the CoRoT Long Run LRc10 looking for planetary candidates. In a first step we removed outliers and trends caused by stellar activity and instrumental problems. Then we applied the Box-fitting Least Squares (BLS) algorithm to detect periodic decreases in luminosity. From all the significative transit detections, we selected the ones that passed different checks. For the 7 planetary candidates found, we applied a new ``ad hoc'' normalization and fitted the orbital parameters, to verify their reliability. Using the stellar temperature information, we could estimate the dimensions that the candidates should have if confirmed. Our research method demonstrated to be sensitive to candidates with hypothetic dimension up to ˜3.5 REarth on stars of mag V≃14.

  8. 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.

  9. Characterizing Earth-like planets: from CoRoT to DARWIN/TPF and beyond

    NASA Astrophysics Data System (ADS)

    Ollivier, M.; Chazelas, B.; Bordé, P.

    2008-08-01

    The detection of terrestrial exoplanets is at its dawn with the detection of the first very low mass planets by microlensing and radial velocimetry. The transit method from space should help getting statistical information about these objects, their abundances, sizes, masses and distance distribution. This goal should be reached by CoRoT and Kepler allowing the next step: the spectral characterization of the potential atmosphere of such planets by the DARWIN/Terrestrial Planet Finder (TPF) mission or similar concepts. In this paper, we describe the key parameters of space missions which will provide in the next decade, their limits, and what can realistically be expected from the next generation of space observatories.

  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. 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.

  12. Solar wind flow angle and geoeffectiveness of corotating interaction regions: First results

    NASA Astrophysics Data System (ADS)

    Rout, Diptiranjan; Chakrabarty, D.; Janardhan, P.; Sekar, R.; Maniya, Vrunda; Pandey, Kuldeep

    2017-05-01

    A total of 43 Corotating Interaction Region (CIR)-induced geomagnetic storms during the unusually deep solar minimum of solar cycle 23 (2006-2010) were identified using a superposed epoch analysis technique. Of these 43 events, detailed cross-spectrum analyses, between the variations in the Z component of the interplanetary magnetic field (IMF Bz) and the equatorial electrojet (EEJ) strength, were performed for 22 events when the daytime EEJ strengths from Jicamarca were available. The analyses revealed that the ˜30 and ˜60 min periodic components in IMF Bz were causally related to the EEJ strength subject to the average solar wind flow being radial to within 6° at L1 during the interval for which EEJ strengths were considered. This investigation elicits the important role of average solar wind azimuthal flow angle in determining the geoeffectiveness of CIR events.

  13. Modelling the Influence of Corotating Interaction Regions on Jovian MeV-electrons

    NASA Astrophysics Data System (ADS)

    Vogt, A.; Effenberger, F.; Fichtner, H.; Heber, B.; Kleimann, J.; Kopp, A.; Potgieter, M. S.; Sternal, O.; Wiengarten, T.

    2015-08-01

    Corotating Interaction Regions (CIRs) are recurrent structures in the solar wind characterized by velocity jumps and a magnetic field compression. Since the 1970s it is known that Jupiter is a quasicontinuous source of MeV-electrons dominating the flux in the inner heliosphere. In connection with CIRs, this flux is modulated mainly by changing propagation conditions in the inner heliosphere. In order to model these recurrent variations in Jovian electron intensity the VLUGR3-Code was used to solve Parker's Transport Equation. The diffusion as well as the solar wind speed are modelled from 0.1 to 50 AU. Two different approaches are used, one derived by Kissmann (2002) and another by Giacalone et al (2002) which was further developed. The simulation results are compared to IMP-8 electron count rates to investigate the differences of the two solar wind models in the propagation code.

  14. Large Amplitude IMF Fluctuations in Corotating Interaction Regions: Ulysses at Midlatitudes

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Ho, Christian M.; Arballo, John K.; Goldstein, Bruce E.; Balogh, Andre

    1995-01-01

    Corotating Interaction Regions (CIRs), formed by high-speed corotating streams interacting with slow speed streams, have been examined from -20 deg to -36 deg heliolatitudes. The high-speed streams emanate from a polar coronal hole that Ulysses eventually becomes fully embedded in as it travels towards the south pole. We find that the trailing portion of the CIR, from the interface surface (IF) to the reverse shock (RS), contains both large amplitude transverse fluctuations and magnitude fluctuations. Similar fluctuations have been previously noted to exist within CIRs detected in the ecliptic plane, but their existence has not been explained. The normalized magnetic field component variances within this portion of the CIR and in the trailing high-speed stream are approximately the same, indicating that the fluctuations in the CIR are compressed Alfven waves. Mirror mode structures with lower intensities are also observed in the trailing portion of the CIR, presumably generated from a local instability driven by free energy associated with compression of the high-speed solar wind plasma. The mixture of these two modes (compressed Alfven waves and mirror modes) plus other modes generated by three wave processes (wave-shock interactions) lead to a lower Alfvenicity within the trailing portion of the CfR than in the high-speed stream proper. The results presented in this paper suggest a mechanism for generation of large amplitude B(sub z) fluctuations within CIRS. Such phenomena have been noted to be responsible for the generation of moderate geomagnetic storms during the declining phase of the solar cycle.

  15. 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.

  16. Large Amplitude IMF Fluctuations in Corotating Interaction Regions: Ulysses at Midlatitudes

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Ho, Christian M.; Arballo, John K.; Goldstein, Bruce E.; Balogh, Andre

    1995-01-01

    Corotating Interaction Regions (CIRs), formed by high-speed corotating streams interacting with slow speed streams, have been examined from -20 deg to -36 deg heliolatitudes. The high-speed streams emanate from a polar coronal hole that Ulysses eventually becomes fully embedded in as it travels towards the south pole. We find that the trailing portion of the CIR, from the interface surface (IF) to the reverse shock (RS), contains both large amplitude transverse fluctuations and magnitude fluctuations. Similar fluctuations have been previously noted to exist within CIRs detected in the ecliptic plane, but their existence has not been explained. The normalized magnetic field component variances within this portion of the CIR and in the trailing high-speed stream are approximately the same, indicating that the fluctuations in the CIR are compressed Alfven waves. Mirror mode structures with lower intensities are also observed in the trailing portion of the CIR, presumably generated from a local instability driven by free energy associated with compression of the high-speed solar wind plasma. The mixture of these two modes (compressed Alfven waves and mirror modes) plus other modes generated by three wave processes (wave-shock interactions) lead to a lower Alfvenicity within the trailing portion of the CfR than in the high-speed stream proper. The results presented in this paper suggest a mechanism for generation of large amplitude B(sub z) fluctuations within CIRS. Such phenomena have been noted to be responsible for the generation of moderate geomagnetic storms during the declining phase of the solar cycle.

  17. 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

  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. Revisiting CoRoT RR Lyrae stars: detection of period doubling and temporal variation of additional frequencies

    NASA Astrophysics Data System (ADS)

    Szabó, R.; Benkő, J. M.; Paparó, M.; Chapellier, E.; Poretti, E.; Baglin, A.; Weiss, W. W.; Kolenberg, K.; Guggenberger, E.; Le Borgne, J.-F.

    2014-10-01

    Context. High-precision, space-based photometric missions like CoRoT and Kepler have revealed new and surprising phenomena in classical variable stars. Such discoveries were the period doubling in RR Lyrae stars and the frequent occurrence of additional periodicities some of which can be explained by radial overtone modes, but others are discordant with the radial eigenfrequency spectrum. Aims: We search for signs of period doubling in CoRoT RR Lyrae stars. The occurrence of this dynamical effect in modulated RR Lyrae stars might help us to gain more information about the mysterious Blazhko effect. The temporal variability of the additional frequencies in representatives of all subtypes of RR Lyrae stars is also investigated. Methods: We preprocess CoRoT light curves by applying trend and jump correction and outlier removal. Standard Fourier technique is used to analyze the frequency content of our targets and follow the time-dependent phenomena. Results: The most comprehensive collection of CoRoT RR Lyrae stars, including new discoveries is presented and analyzed. We found alternating maxima and in some cases half-integer frequencies in four CoRoT Blazhko RR Lyrae stars, as clear signs of the presence of period doubling. This reinforces that period doubling is an important ingredient for understanding the Blazhko effect - a premise we derived previously from the Kepler RR Lyrae sample. As expected, period doubling is detectable only for short time intervals in most modulated RRab stars. Our results show that the temporal variability of the additional frequencies in all RR Lyrae subtypes is ubiquitous. The ephemeral nature and the highly variable amplitude of these variations suggest a complex underlying dynamics of and an intricate interplay between radial and possibly nonradial modes in RR Lyrae stars. The omnipresence of additional modes in all types of RR Lyrae - except in non-modulated RRab stars - implies that asteroseismology of these objects should be

  20. The vertical structure of oceanic Rossby waves: a comparison of high-resolution model data to theoretical vertical structures

    NASA Astrophysics Data System (ADS)

    Hunt, F. K.; Tailleux, R.; Hirschi, J. J.-M.

    2011-05-01

    Tests of the new Rossby wave theories that have been developed over the past decade to account for discrepancies between theoretical wave speeds and those observed by satellite altimeters have focused primarily on the surface signature of such waves. It appears, however, that the surface signature of the waves acts only as a rather weak constraint, and that information on the vertical structure of the waves is required to better discriminate between competing theories. Due to the lack of 3-D observations, this paper uses high-resolution model data to construct realistic vertical structures of Rossby waves and compares these to structures predicted by theory. The meridional velocity of a section at 24° S in the Atlantic Ocean is pre-processed using the Radon transform to select the dominant westward signal. Normalized profiles are then constructed using three complementary methods based respectively on: (1) averaging vertical profiles of velocity, (2) diagnosing the amplitude of the Radon transform of the westward propagating signal at different depths, and (3) EOF analysis. These profiles are compared to profiles calculated using four different Rossby wave theories: standard linear theory (SLT), SLT plus mean flow, SLT plus topographic effects, and theory including mean flow and topographic effects. The model data supports the classical theoretical assumption that westward propagating signals have a well-defined vertical modal structure associated with a phase speed independent of depth, in contrast with the conclusions of a recent study using the same model. The model structures were surface intensified, with a sign reversal at depth in some regions, notably occurring at shallower depths in the East Atlantic. SLT provides a good fit to the model structures in the top 300 m, but grossly overestimates the sign reversal at depth. The addition of mean flow slightly improves the latter issue, but is too surface intensified. SLT plus topography rectifies the

  1. The vertical structure of oceanic Rossby waves: a comparison of high-resolution model data to theoretical vertical structures

    NASA Astrophysics Data System (ADS)

    Hunt, F. K.; Tailleux, R.; Hirschi, J. J.-M.

    2012-01-01

    Tests of the new Rossby wave theories that have been developed over the past decade to account for discrepancies between theoretical wave speeds and those observed by satellite altimeters have focused primarily on the surface signature of such waves. It appears, however, that the surface signature of the waves acts only as a rather weak constraint, and that information on the vertical structure of the waves is required to better discriminate between competing theories. Due to the lack of 3-D observations, this paper uses high-resolution model data to construct realistic vertical structures of Rossby waves and compares these to structures predicted by theory. The meridional velocity of a section at 24° S in the Atlantic Ocean is pre-processed using the Radon transform to select the dominant westward signal. Normalized profiles are then constructed using three complementary methods based respectively on: (1) averaging vertical profiles of velocity, (2) diagnosing the amplitude of the Radon transform of the westward propagating signal at different depths, and (3) EOF analysis. These profiles are compared to profiles calculated using four different Rossby wave theories: standard linear theory (SLT), SLT plus mean flow, SLT plus topographic effects, and theory including mean flow and topographic effects. Our results support the classical theoretical assumption that westward propagating signals have a well-defined vertical modal structure associated with a phase speed independent of depth, in contrast with the conclusions of a recent study using the same model but for different locations in the North Atlantic. The model structures are in general surface intensified, with a sign reversal at depth in some regions, notably occurring at shallower depths in the East Atlantic. SLT provides a good fit to the model structures in the top 300 m, but grossly overestimates the sign reversal at depth. The addition of mean flow slightly improves the latter issue, but is too surface

  2. 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

  3. 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

  4. 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

  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. 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).

  7. Corotating Interaction Regions in Stellar Winds: Particle Acceleration and Non-thermal Radio Emission in Hot Stars

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1985-01-01

    A co-rotating interaction region (CIR) forms in a stellar wind when a fast stream from a rotating star overtakes a slow stream. The CIR's were studied in detail in the solar wind over the past decade primarily because they are efficient sources of particle acceleration. Here, CIR's in OB star winds are used to explain two properties of such winds: deposition of non-radiative energy in the wind far from the stellar surfaces and acceleration of non-thermal particles.

  8. Pulsations in the late-type Be star HD 50 209 detected by CoRoT

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

    Context: The presence of pulsations in late-type Be stars is still a matter of controversy. It constitutes an important issue to establish the relationship between non-radial pulsations and the mass-loss mechanism in Be stars. Aims: To contribute to this discussion, we analyse the photometric time series of the B8IVe star HD 50 209 observed by the CoRoT mission in the seismology field. Methods: We use standard Fourier techniques and linear and non-linear least squares fitting methods to analyse the CoRoT light curve. In addition, we applied detailed modelling of high-resolution spectra to obtain the fundamental physical parameters of the star. Results: We have found four frequencies which correspond to gravity modes with azimuthal order m=0,-1,-2,-3 with the same pulsational frequency in the co-rotating frame. We also found a rotational period with a frequency of 0.679 cd-1 (7.754 μHz). Conclusions: HD 50 209 is a pulsating Be star as expected from its position in the HR diagram, close to the SPB instability strip. Based on observations made with the CoRoT satellite, with FEROS at the 2.2 m telescope of the La Silla Observatory under the ESO Large Programme LP178.D-0361 and with Narval at the Télescope Bernard Lyot of the Pic du Midi Observatory. Current address: Valencian International University (VIU), José Pradas Gallen s/n, 12006 Castellón, Spain. Current address: Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot; CEA, IRFU, SAp, centre de Saclay, 91191 Gif-sur-Yvette, France.

  9. Disentangling planetary and stellar activity features in the CoRoT-2 light curve

    NASA Astrophysics Data System (ADS)

    Bruno, G.; Deleuil, M.; Almenara, J.-M.; Barros, S. C. C.; Lanza, A. F.; Montalto, M.; Boisse, I.; Santerne, A.; Lagrange, A.-M.; Meunier, N.

    2016-11-01

    Aims: Stellar activity is an important source of systematic errors and uncertainties in the characterization of exoplanets. Most of the techniques used to correct for this activity focus on an ad hoc data reduction. Methods: We have developed a software for the combined fit of transits and stellar activity features in high-precision long-duration photometry. Our aim is to take advantage of the modelling to derive correct stellar and planetary parameters, even in the case of strong stellar activity. Results: We use an analytic approach to model the light curve. The code KSint, modified by adding the evolution of active regions, is implemented into our Bayesian modelling package PASTIS. The code is then applied to the light curve of CoRoT-2. The light curve is divided in segments to reduce the number of free parameters needed by the fit. We perform a Markov chain Monte Carlo analysis in two ways. In the first, we perform a global and independent modelling of each segment of the light curve, transits are not normalized and are fitted together with the activity features, and occulted features are taken into account during the transit fit. In the second, we normalize the transits with a model of the non-occulted activity features, and then we apply a standard transit fit, which does not take the occulted features into account. Conclusions: Our model recovers the activity features coverage of the stellar surface and different rotation periods for different features. We find variations in the transit parameters of different segments and show that they are likely due to the division applied to the light curve. Neglecting stellar activity or even only bright spots while normalizing the transits yields a 1.2σ larger and 2.3σ smaller transit depth, respectively. The stellar density also presents up to 2.5σ differences depending on the normalization technique. Our analysis confirms the inflated radius of the planet (1.475 ± 0.031RJ) found by other authors. We show that

  10. Hydrodynamical Simulations of Corotating Interaction Regions and Discrete Absorption Components in Rotating O-Star Winds

    NASA Astrophysics Data System (ADS)

    Cranmer, Steven R.; Owocki, Stanley P.

    1996-05-01

    We present two-dimensional hydrodynamical simulations of corotating interaction regions (CIRs) in the wind from a rotating 0 star, together with resulting synthetic line profiles showing discrete absorption components (DACs). For computational tractability, we use a local, Sobolev treatment of the radiative force, which suppresses the small-scale instability intrinsic to line driving but still allows us to model the dynamics of large-scale wind structure. As a first step toward modeling the wind response to large-scale base perturbations (e.g., from surface magnetic fields or nonradial pulsations), the structure here is explicitly induced by localized increases or decreases in the radiative force, as would result from a bright or dark "star spot" near the star's equator. We find that bright spots with enhanced driving generate high-density, low-speed streams, while dark spots generate low-density, high-speed streams. CIRs form where fast material collides with slow material; e.g., at the leading (trailing) edge of a stream from a dark (bright) spot, often steepening into shocks. The unperturbed supersonic wind obliquely impacts the high-density CIR and sends back a nonlinear signal that takes the form of a sharp propagating discontinuity ("kink" or "plateau") in the radial velocity gradient. In the wind's comoving frame, these features propagate inward at the fast characteristic speed derived by Abbott for radiatively modified acoustic waves, but because this is generally only slightly less than the outward wind speed, the features evolve only slowly outward in the star's frame. We find that these slow kinks, rather than the CIRs themselves, are more likely to result in DACs in the absorption troughs of unsaturated P Cygni line profiles. Because the hydrodynamic structure settles to a steady state in a frame corotating with the star, the more tightly spiraled kinks sweep by an observer on a longer timescale than material moving with the wind itself. This is in

  11. Galactic archaeology with asteroseismology and spectroscopy: Red giants observed by CoRoT and APOGEE

    NASA Astrophysics Data System (ADS)

    Anders, F.; Chiappini, C.; Rodrigues, T. S.; Miglio, A.; Montalbán, J.; Mosser, B.; Girardi, L.; Valentini, M.; Noels, A.; Morel, T.; Johnson, J. A.; Schultheis, M.; Baudin, F.; de Assis Peralta, R.; Hekker, S.; Themeßl, N.; Kallinger, T.; García, R. A.; Mathur, S.; Baglin, A.; Santiago, B. X.; Martig, M.; Minchev, I.; Steinmetz, M.; da Costa, L. N.; Maia, M. A. G.; Allende Prieto, C.; Cunha, K.; Beers, T. C.; Epstein, C.; García Pérez, A. E.; García-Hernández, D. A.; Harding, P.; Holtzman, J.; Majewski, S. R.; Mészáros, Sz.; Nidever, D.; Pan, K.; Pinsonneault, M.; Schiavon, R. P.; Schneider, D. P.; Shetrone, M. D.; Stassun, K.; Zamora, O.; Zasowski, G.

    2017-01-01

    With the advent of the space missions CoRoT and Kepler, it has recently become feasible to determine precise asteroseismic masses and relative ages for large samples of red giant stars. We present the CoRoGEE dataset, obtained from CoRoT light curves for 606 red giants in two fields of the Galactic disc that have been co-observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). We used the Bayesian parameter estimation code PARAM to calculate distances, extinctions, masses, and ages for these stars in a homogeneous analysis, resulting in relative statistical uncertainties of ≲2% in distance, 4% in radius, 9% in mass and 25% in age. We also assessed systematic age uncertainties stemming from different input physics and mass loss. We discuss the correlation between ages and chemical abundance patterns of field stars over a broad radial range of the Milky Way disc (5 kpc

  12. Numerical model for zonal flow generation by magnetized Rossby waves in the ionosphere with the background shear flow

    NASA Astrophysics Data System (ADS)

    Kharshiladze, O. A.; Chargazia, Kh.

    2017-03-01

    A theoretical-numerical description of zonal flow generation in the turbulent ionosphere by controlled inhomogeneous background wind is given. The generalized Charney-Obukhov equation, which describes the nonlinear interaction of five different-scale modes (primary modes, relatively short-wave ultra-low frequency (ULF) magnetized Rossby waves (MRWs) (pumping waves), two satellites of these MRWs, long-wave zonal mode, and large-scale background shear flows (inhomogeneous wind)) is used. New features of energy transfer from relatively small-scale waves and the background shear flow into that of largescale zonal flows and nonlinear self-organization of the five-wave collective activity in the ionospheric medium are identified based on the numerical solution of the corresponding system of equations for perturbation amplitudes (generalized eigenvalue problems). It is shown that if there is the background shear flow with a moderate amplitude growth the modulation instability increment and intensifies the zonal flow generation, while a very strong shear flow significantly reduces the modulation instability increment and can even suppress the generation process.

  13. Inertia-less convectively-driven dynamo models in the limit of low Rossby number and large Prandtl number

    NASA Astrophysics Data System (ADS)

    Calkins, Michael A.; Julien, Keith; Tobias, Steven M.

    2017-05-01

    Compositional convection is thought to be an important energy source for magnetic field generation within planetary interiors. The Prandtl number, Pr, characterizing compositional convection is significantly larger than unity, suggesting that the inertial force may not be important on the small scales of convection as long as the buoyancy force is not too strong. We develop asymptotic dynamo models for the case of small Rossby number and large Prandtl number in which inertia is absent on the convective scale. The relevant diffusivity parameter for this limit is the compositional Roberts number, q = D / η , which is the ratio of compositional and magnetic diffusivities. Dynamo models are developed for both order one q and the more geophysically relevant low q limit. For both cases the ratio of magnetic to kinetic energy densities, M, is asymptotically large and reflects the fact that Alfvén waves have been filtered from the dynamics. Along with previous investigations of asymptotic dynamo models for Pr = O (1) , our results show that the ratio M is not a useful indicator of dominant force balances in the momentum equation since many different asymptotic limits of M can be obtained without changing the leading order geostrophic balance. Furthermore, the present models show that inertia is not a requirement for driving low q, large-scale dynamos.

  14. 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.

  15. 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.

  16. Influence of the background state on Rossby wave propagation into the Great Lakes region based on reanalysis data and model simulations

    NASA Astrophysics Data System (ADS)

    Holman, K.; Lorenz, D. J.; Notaro, M.

    2012-12-01

    Fluctuations in the water levels of the Great Lakes have major economical and environmental impacts. On average, warm-season (May-September) changes in the water level of Lake Superior, the largest of the Great Lakes by surface area and volume, are largely driven by over-lake precipitation. The use of one-point lagged correlation maps between monthly over-lake precipitation and the 300-hPa meridional wind demonstrates that over-lake precipitation on Lake Superior is associated with a Rossby wave train located across the North Pacific and U.S. Further analysis suggests that the origin and pathway of the Rossby wave train depends strongly on season and appears related to the time-mean, upper-level flow (or jet stream). During summer and early fall, the Pacific jet is relatively sharp and acts as a waveguide, such that Rossby wave trains traversing the Great Lakes region do not follow a great circle. Instead, disturbances originate in the Western Pacific and travel along the Pacific jet, remaining at approximately 50°N. At other times of the year, the Pacific jet is relatively broad in the eastern Pacific (although with greater maximum speed). This broad jet allows more wave activity originating in the tropics to penetrate into the mid-latitudes and influence Lake Superior precipitation. In twentieth century simulations from the CMIP3 models, Rossby wave train propagation can be significantly different. Unlike observations, some models do not produce a sharp, well-defined jet across the Pacific Ocean during summer and fall. In these models, waves affecting Lake Superior precipitation originate in the tropics. Conversely, some CMIP3 models tend to produce an elongated jet across the Pacific Ocean during the early winter months, which acts as a strong waveguide for disturbances crossing the Great Lakes region. As a result, these disturbances tend to originate over the Asian continent and appear trapped in the jet stream. Collectively, observations and model results

  17. Detecting planets in Kepler lightcurves using methods developed for CoRoT.

    NASA Astrophysics Data System (ADS)

    Grziwa, S.; Korth, J.; Pätzold, M.

    2011-10-01

    Launched in March 2009, Kepler is the second space telescope dedicated to the search for extrasolar planets. NASA released 150.000 lightcurves to the public in 2010 and announced that Kepler has found 1.235 candidates. The Rhenish Institute for Environmental Research (RIU-PF) is one of the detection groups from the CoRoT space mission. RIU-PF developed the software package EXOTRANS for the detection of transits in stellar lightcurves. EXOTRANS is designed for the fast automated processing of huge amounts of data and was easily adapted to the analysis of Kepler lightcurves. The use of different techniques and philosophies helps to find more candidates and to rule out others. We present the analysis of the Kepler lightcurves with EXOTRANS. Results of our filter (trend, harmonic) and detection (dcBLS) techniques are compared with the techniques used by Kepler (PDC, TPS). The different approaches to rule out false positives are discussed and additional candidates found by EXOTRANS are presented.

  18. 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.

  19. Cosmic-Ray Transport in Heliospheric Magnetic Structures. II. Modeling Particle Transport through Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Kopp, Andreas; Wiengarten, Tobias; Fichtner, Horst; Effenberger, Frederic; Kühl, Patrick; Heber, Bernd; Raath, Jan-Louis; Potgieter, Marius S.

    2017-03-01

    The transport of cosmic rays (CRs) in the heliosphere is determined by the properties of the solar wind plasma. The heliospheric plasma environment has been probed by spacecraft for decades and provides a unique opportunity for testing transport theories. Of particular interest for the three-dimensional (3D) heliospheric CR transport are structures such as corotating interaction regions (CIRs), which, due to the enhancement of the magnetic field strength and magnetic fluctuations within and due to the associated shocks as well as stream interfaces, do influence the CR diffusion and drift. In a three-fold series of papers, we investigate these effects by modeling inner-heliospheric solar wind conditions with the numerical magnetohydrodynamic (MHD) framework Cronos (Wiengarten et al., referred as Paper I), and the results serve as input to a transport code employing a stochastic differential equation approach (this paper). While, in Paper I, we presented results from 3D simulations with Cronos, the MHD output is now taken as an input to the CR transport modeling. We discuss the diffusion and drift behavior of Galactic cosmic rays using the example of different theories, and study the effects of CIRs on these transport processes. In particular, we point out the wide range of possible particle fluxes at a given point in space resulting from these different theories. The restriction of this variety by fitting the numerical results to spacecraft data will be the subject of the third paper of this series.

  20. 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.

  1. Existence of Corotating and Counter-Rotating Vortex Pairs for Active Scalar Equations

    NASA Astrophysics Data System (ADS)

    Hmidi, Taoufik; Mateu, Joan

    2017-03-01

    In this paper, we study the existence of corotating and counter-rotating pairs of simply connected patches for Euler equations and the {(SQG)_{α}} equations with {α in (0,1)}. From the numerical experiments implemented for Euler equations in Deem and Zabusky (Phys Rev Lett 40(13):859-862, 1978), Pierrehumbert (J Fluid Mech 99:129-144, 1980), Saffman and Szeto (Phys Fluids 23(12):2339-2342, 1980) it is conjectured the existence of a curve of steady vortex pairs passing through the point vortex pairs. There are some analytical proofs based on variational principle (Keady in J Aust Math Soc Ser B 26:487-502, 1985; Turkington in Nonlinear Anal Theory Methods Appl 9(4):351-369, 1985); however, they do not give enough information about the pairs, such as the uniqueness or the topological structure of each single vortex. We intend in this paper to give direct proofs confirming the numerical experiments and extend these results for the {(SQG)_{α}} equation when {α in (0,1)}. The proofs rely on the contour dynamics equations combined with a desingularization of the point vortex pairs and the application of the implicit function theorem.

  2. Dynamics of Quasi 2D and 3D Co-rotating Vortex Merger

    NASA Astrophysics Data System (ADS)

    Khandekar, Akshay; Jacob, Jamey

    2013-11-01

    Merger of vortices is examined experimentally to compare the merger of slender parallel vortices generated either coincidentally or continuously. It is known that like-sign vortices rotate around a common center of circulation and merger between the vortices may occur under certain conditions. This merger is dependent on the strength of the vortex circulation, distance of separation between the centers of the two vortices, ReΓ , and vorticity distribution. Quasi-2D and 3D experimental data is examined and merger relations are derived. The former uses high aspect ratio rotating paddles in a tank and while the latter are from wing-tip vortices in a wind tunnel. The vortex merger tank generates slender co-rotating vortices and are examined using PIV, while in the wind tunnel two opposing wings are arranged at opposite angles of attack to generate a pair of vortices that merge downstream. A 5-hole probe is used to obtain 3D velocity vectors via wake survey, along with PIV. The procedure is performed in the wake at different distances to observe merger under different conditions. Temporally and spatially dependent relations in quasi-2D and 3D vortex merger are derived. Merger behavior is generally similar between the cases, but instabilities along quasi-2D vortices may affect.

  3. Corotating high-speed solar-wind streams and recurrent cosmic ray modulation

    NASA Astrophysics Data System (ADS)

    Singh, Y. P.; Badruddin

    2007-05-01

    We studied the solar magnetic cycle dependence of cosmic ray depressions due to the corotating high-speed solar wind streams (CSWS) during different polarity states of the heliosphere. The daily averaged cosmic ray intensity data from Climax, Oulu, and Thule neutron monitors together with simultaneous solar wind plasma and field data were subjected to the superposed epoch analysis with respect to CSWS start time. These analyses were carried out separately in different polarity states of the heliosphere A < 0 and A > 0 during solar minimum as well as during the periods of variable solar activity. Although the average variations in the solar wind velocity, IMF strength, and its variance are almost similar, the amplitudes of CSWS-associated cosmic ray depressions are quite different during different polarity epochs; they are larger during A > 0 than A < 0 periods. Further, correlation analysis between cosmic ray intensity and solar wind velocity during CSWS shows differences in their relationship during A > 0 and A < 0; they are much better during A > 0 than A < 0. Two other solar wind parameters, IMF strength and its variance, do not show a significant relationship with cosmic ray intensity change through the passage of these streams, although the initial depression coincides the enhancement of the two parameters. These results are discussed in the light of existing models of galactic cosmic ray modulation.

  4. The physics of pressure variation in microchannels within corotating or static discs

    NASA Astrophysics Data System (ADS)

    Guha, Abhijit; Sengupta, Sayantan

    2016-10-01

    We formulate a comprehensive analysis for the radial pressure variation in flow through microchannels within corotating (or static) discs, which is important for its fundamental value and application potential in macrofluidic and microfluidic devices. The uniqueness and utility of the present approach emanate from our ability to describe the physics completely in terms of non-dimensional numbers and to determine quantitatively the separate roles of inertia, centrifugal force, Coriolis force, and viscous effects in the overall radial pressure difference (Δpio). It is established here that the aspect ratio (ratio of inter-disc spacing and disc radius) plays only a secondary role as an independent parameter, its major role being contained within a newly identified dynamic similarity number (Ds). For radial inflow, it is shown that the magnitude of Δpio decreases monotonically as the tangential speed ratio (γ) increases but exhibits a minima when Ds is varied. For radial outflow, it is shown that Δpio increases monotonically as the flow coefficient (ϕ) decreases but evinces a maxima when Ds is varied. It is further shown that for the radial inflow case, the minima in the magnitude of Δpio exist even when the rotational speed of the discs is reduced to zero (static discs). The demonstrated existence of these extrema (i.e., minima for radial inflow and maxima for radial outflow) creates the scope for device optimization.

  5. Large-deflection statics analysis of active cardiac catheters through co-rotational modelling.

    PubMed

    Peng Qi; Chen Qiu; Mehndiratta, Aadarsh; I-Ming Chen; Haoyong Yu

    2016-08-01

    This paper presents a co-rotational concept for large-deflection formulation of cardiac catheters. Using this approach, the catheter is first discretized with a number of equal length beam elements and nodes, and the rigid body motions of an individual beam element are separated from its deformations. Therefore, it is adequate for modelling arbitrarily large deflections of a catheter with linear elastic analysis at the local element level. A novel design of active cardiac catheter of 9 Fr in diameter at the beginning of the paper is proposed, which is based on the contra-rotating double helix patterns and is improved from the previous prototypes. The modelling section is followed by MATLAB simulations of various deflections when the catheter is exerted different types of loads. This proves the feasibility of the presented modelling approach. To the best knowledge of the authors, it is the first to utilize this methodology for large-deflection static analysis of the catheter, which will enable more accurate control of robot-assisted cardiac catheterization procedures. Future work would include further experimental validations.

  6. Mechanistic modeling of modular co-rotating twin-screw extruders.

    PubMed

    Eitzlmayr, Andreas; Koscher, Gerold; Reynolds, Gavin; Huang, Zhenyu; Booth, Jonathan; Shering, Philip; Khinast, Johannes

    2014-10-20

    In this study, we present a one-dimensional (1D) model of the metering zone of a modular, co-rotating twin-screw extruder for pharmaceutical hot melt extrusion (HME). The model accounts for filling ratio, pressure, melt temperature in screw channels and gaps, driving power, torque and the residence time distribution (RTD). It requires two empirical parameters for each screw element to be determined experimentally or numerically using computational fluid dynamics (CFD). The required Nusselt correlation for the heat transfer to the barrel was determined from experimental data. We present results for a fluid with a constant viscosity in comparison to literature data obtained from CFD simulations. Moreover, we show how to incorporate the rheology of a typical, non-Newtonian polymer melt, and present results in comparison to measurements. For both cases, we achieved excellent agreement. Furthermore, we present results for the RTD, based on experimental data from the literature, and found good agreement with simulations, in which the entire HME process was approximated with the metering model, assuming a constant viscosity for the polymer melt.

  7. The changing phases of extrasolar planet CoRoT-1b.

    PubMed

    Snellen, Ignas A G; de Mooij, Ernst J W; Albrecht, Simon

    2009-05-28

    Hot Jupiters are a class of extrasolar planet that orbit their parent stars at very short distances. They are expected to be tidally locked, which can lead to a large temperature difference between their daysides and nightsides. Infrared observations of eclipsing systems have yielded dayside temperatures for a number of transiting planets. The day-night contrast of the transiting extrasolar planet HD 189733b was 'mapped' using infrared observations. It is expected that the contrast between the daysides and nightsides of hot Jupiters is much higher at visual wavelengths, shorter than that of the peak emission, and could be further enhanced by reflected stellar light. Here we report the analysis of optical photometric data obtained over 36 planetary orbits of the transiting hot Jupiter CoRoT-1b. The data are consistent with the nightside hemisphere of the planet being entirely black, with the dayside flux dominating the optical phase curve. This means that at optical wavelengths the planet's phase variation is just as we see it for the interior planets in the Solar System. The data allow for only a small fraction of reflected light, corresponding to a geometric albedo of <0.20.

  8. 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

  9. A singular vortex Rossby wave packet within a rapidly rotating vortex

    NASA Astrophysics Data System (ADS)

    Caillol, Philippe

    2017-04-01

    This paper describes the quasi-steady régime attained by a rapidly rotating vortex after a wave packet has interacted with it. We consider singular, nonlinear, helical, and shear asymmetric modes within a linearly stable, columnar, axisymmetric, and dry vortex in the f-plane. The normal modes enter resonance with the vortex at a certain radius rc, where the phase angular speed is equal to the rotation frequency. The related singularity in the modal equation at rc strongly modifies the flow in the 3D helical critical layer, the region where the wave/vortex interaction occurs. This interaction induces a secondary mean flow of higher amplitude than the wave packet and that diffuses at either side of the critical layer inside two spiral diffusion boundary layers. We derive the leading-order equations of the system of nonlinear coupled partial differential equations that govern the slowly evolving amplitudes of the wave packet and induced mean flow a long time after this interaction started. We show that the critical layer imposes its proper scalings and evolution equations; in particular, two slow times are involved, the faster being secular. This system leads to a more complex dynamics with respect to the previous studies on wave packets where this coupling was omitted and where, for instance, a nonlinear Schrödinger equation was derived [D. J. Benney and S. A. Maslowe, "The evolution in space and time of nonlinear waves in parallel shear flows," Stud. Appl. Math. 54, 181 (1975)]. Matched asymptotic expansion method lets appear that the neutral modes are distorted. The main outcome is that a stronger wave/vortex interaction takes place when a wave packet is considered with respect to the case of a single mode. Numerical simulations of the leading-order inviscid Burgers-like equations of the derived system show that the wave packet rapidly breaks and that the vortex, after intensifying in the transition stage, is substantially weakened before the breaking onset. This

  10. 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

  11. Spitzer Infrared Observations and Independent Validation of the Transiting Super-Earth CoRoT-7 b

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    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 μm and 8.0 μm 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 μm, 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 μm did not yield a significant detection. The 4.5 μm 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. Our Spitzer

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  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 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.

  18. 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.

  19. Investigating the origin of cyclical wind variability in hot massive stars - II. Hydrodynamical simulations of corotating interaction regions using realistic spot parameters for the O giant ξ Persei

    NASA Astrophysics Data System (ADS)

    David-Uraz, A.; Owocki, S. P.; Wade, G. A.; Sundqvist, J. O.; Kee, N. D.

    2017-09-01

    OB stars exhibit various types of spectral variability historically associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These features have been proposed to be caused either by magnetic fields or non-radial pulsations. In this second paper of this series, we revisit the canonical phenomenological hydrodynamical modelling used to explain the formation of DACs by taking into account modern observations and more realistic theoretical predictions. Using constraints on putative bright spots located on the surface of the O giant ξ Persei derived from high precision space-based broad-band optical photometry obtained with the Microvariability and Oscillations of Stars (MOST) space telescope, we generate 2D hydrodynamical simulations of corotating interaction regions in its wind. We then compute synthetic ultraviolet (UV) resonance line profiles using Sobolev Exact Integration and compare them with historical timeseries obtained by the International Ultraviolet Explorer (IUE) to evaluate if the observed behaviour of ξ Persei's DACs is reproduced. Testing three different models of spot size and strength, we find that the classical pattern of variability can be successfully reproduced for two of them: the model with the smallest spots yields absorption features that are incompatible with observations. Furthermore, we test the effect of the radial dependence of ionization levels on line driving, but cannot conclusively assess the importance of this factor. In conclusion, this study self-consistently links optical photometry and UV spectroscopy, paving the way to a better understanding of cyclical wind variability in massive stars in the context of the bright spot paradigm.

  20. 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

  1. Source Population and Acceleration Location of Suprathermal Heavy Ions in Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    We have analyzed the ∼20–320 keV nucleon‑1 suprathermal (ST) heavy ion abundances in 41 corotating interaction regions (CIRs) observed by the Wind spacecraft from 1995 January to 2008 December. Our results are: (1) the CIR Fe/CNO and NeS/CNO ratios vary with the sunspot number, with values being closer to average solar energetic particle event values during solar maxima and lower than nominal solar wind values during solar minima. The physical mechanism responsible for the depleted abundances during solar minimum remains an open question. (2) The Fe/CNO increases with energy in the 6 events that occurred during solar maximum, while no such trends are observed for the 35 events during solar minimum. (3) The Fe/CNO shows no correlation with the average solar wind speed. (4) The Fe/CNO is well correlated with the corresponding upstream ∼20–320 keV nucleon‑1 Fe/CNO and not with the solar wind Fe/O measured by ACE in 31 events. Using the correlations between the upstream ∼20–40 keV nucleon‑1 Fe/CNO and the ∼20–320 keV nucleon‑1 Fe/CNO in CIRs, we estimate that, on average, the ST particles traveled ∼2 au along the nominal Parker spiral field line, which corresponds to upper limits for the radial distance of the source or acceleration location of ∼1 au beyond Earth orbit. Our results are consistent with those obtained from recent surveys, and confirm that CIR ST heavy ions are accelerated more locally, and are at odds with the traditional viewpoint that CIR ions seen at 1 au are bulk solar wind ions accelerated between 3 and 5 au.

  2. Halting Migration: Numerical Calculations of Corotation Torques in the Weakly Nonlinear Regime

    NASA Astrophysics Data System (ADS)

    Duffell, Paul C.

    2015-06-01

    Planets in their formative years can migrate due to the influence of gravitational torques in the protoplanetary disk they inhabit. For low-mass planets in an isothermal disk, it is known that there is a strong negative torque on the planet due to its linear perturbation to the disk, causing fast inward migration. The current investigation demonstrates that in these same isothermal disks, for intermediate-mass planets, there is a strong positive nonlinear corotation torque due to the effects of gas being pulled through a gap on horseshoe orbits. For intermediate-mass planets, this positive torque can partially or completely cancel the linear (Type I) torque, leading to slower or outward migration, even in an isothermal disk. The effect is most significant for super-Earth and sub-Jovian planets, during the transition from a low-mass linear perturber to a nonlinear gap-opening planet, when the planet has opened a so-called “partial gap,” though the precise values of these transition masses depend sensitively on the disk model (density profile, viscosity, and disk aspect ratio). In this study, numerical calculations of planet-disk interactions calculate these torques explicitly, and scalings are empirically constructed for migration rates in this weakly nonlinear regime. These results find outward migration is possible for planets with masses in the range 20-100 {M}\\oplus , though this range depends on the disk model considered. In the disk models where torque reversal occurs, the critical planet-to-star mass ratio for torque reversal was found to have the robust scaling {q}{crit}\\propto \\sqrt{α }{(h/r)}3, where α is the dimensionless viscosity parameter and h/r is the disk aspect ratio.

  3. The evolution of co-rotating vortices in a canonical boundary layer with inclined jets

    NASA Astrophysics Data System (ADS)

    Zhang, Xin

    2003-12-01

    The evolution of co-rotating streamwise vortices in a canonical flat plate turbulent boundary layer (thickness of the boundary layer δ0.99=25 mm) is studied. The vortices are produced by an array of inclined jets (diameter D=14 mm) with the same orientation (skew angle β and pitch angle α of 45°). The focus of the investigation is on the immediate vicinity of the jet exit and downstream locations up to 40 D. The Reynolds number based on the diameter of the jet nozzle ranges from 9700 to 29 000, at various jet speed ratios. The main method of investigation is laser Doppler anemometry. Both mean and statistic data are collected and analyzed. The streamwise vortices are a product of complex fluid flow process, featuring horseshoe vortices in front of the nozzle exit, recirculating flow to the lee side of the nozzle, contra-rotating vortices from the rolling up of vortex sheet around the jet, strong and induced spanwise flow. Two types of streamwise vortices are produced: (a) weak vortices at a jet speed ratio λ of 0.5 located close to the wall and featuring diametrically opposed, secondary, near-wall flows in between the vortices, (b) strong vortices at higher jet speed ratio featuring significant spanwise movement. The vortices are accompanied by high levels of turbulence, with distinct normal and shear stress distributions. Both turbulence production and convection play important roles in defining the normal stress but only the turbulence production is important in determining the shear stress.

  4. 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.

  5. Energetic electron precipitation in weak to moderate corotating interaction region-driven storms

    NASA Astrophysics Data System (ADS)

    Ødegaard, Linn-Kristine Glesnes; Tyssøy, Hilde Nesse; Søraas, Finn; Stadsnes, Johan; Sandanger, Marit Irene

    2017-03-01

    High-energy electron precipitation from the radiation belts can penetrate deep into the mesosphere and increase the production rate of NOx and HOx, which in turn will reduce ozone in catalytic processes. The mechanisms for acceleration and loss of electrons in the radiation belts are not fully understood, and most of the measurements of the precipitating flux into the atmosphere have been insufficient for estimating the loss cone flux. In the present study the electron flux measured by the NOAA POES Medium Energy Proton and Electron Detectors 0° and 90° detectors is combined together with theory of pitch angle diffusion by wave-particle interaction to quantify the electron flux lost below 120 km altitude. Using this method, 41 weak and moderate geomagnetic storms caused by corotating interaction regions during 2006-2010 are studied. The dependence of the energetic electron precipitation fluxes upon solar wind parameters and geomagnetic indices is investigated. Nine storms give increased precipitation of >˜750 keV electrons. Nineteen storms increase the precipitation of >˜300 keV electrons, but not the >˜750 keV population. Thirteen storms either do not change or deplete the fluxes at those energies. Storms that have an increase in the flux of electrons with energy >˜300 keV are characterized by an elevated solar wind velocity for a longer period compared to the storms that do not. Storms with increased precipitation of >˜750 keV flux are distinguished by higher-energy input from the solar wind quantified by the ɛ parameter and corresponding higher geomagnetic activity.

  6. 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.

  7. 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

  8. 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

  9. A formulation of three-dimensional residual mean flow and wave activity flux applicable to both to Rossby waves and gravity waves

    NASA Astrophysics Data System (ADS)

    Kinoshita, T.; Sato, K.

    2012-12-01

    The Transformed Eulerian-Mean (TEM) equations formulated by Andrews and McIntyre (1976, 1978) has been widely used to examine wave-mean flow interaction in the meridional cross section. Although a lot of efforts have been made to generalize the TEM equations to three dimensions so far, formulae derived by previous studies are applicable to particular waves, mainly Rossby waves on the quasi-geostrophic (QG) equations or inertia-gravity waves on the primitive equations. This study has newly formulated three-dimensional (3D) TEM equations which are applicable to both Rossby waves and gravity waves. The formulae can be used to examine the 3D material transport driven by these waves. Moreover, two kinds of 3D wave activity flux have been derived respectively for describing the wave force to the mean flow and for the wave propagation. The residual mean flow is expressed with the sum of the Eulerian-mean flow and the Stokes drift in the 2D TEM equations. Thus, a formulation is made for the 3D Stokes drift on the primitive equation (PRSD) from its original definition using a small amplitude theory for a slowly-varying mean flow. The PRSD is equivalent to the 3D Stokes drift derived by Kinoshita et al. (2010) for gravity waves for the constant Coriolis parameter and to the 3D QG Stokes drift which is also derived in this study for the small Rossby number limit. The 3D wave activity flux (3D-flux-M), whose divergence corresponds to the wave force, is derived by using PRSD. The 3D residual mean flow associated with synoptic-scale wave disturbances in the upper troposphere in April is investigated by applying the new formulae to ERA-Interim data. It is found that the sum of time-mean unbalanced flow and PRSD is southward in the east end of the storm track although it is northward in the west as is consistent with the 2D residual flow. A case study is also made for dominant gravity waves around the Southern Andes by applying the PRSD and 3D-flux-M to the simulation data of a

  10. 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

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. ENSO to multi-decadal time scale changes in East Australian Current transports and Fort Denison sea level: Oceanic Rossby waves as the connecting mechanism

    NASA Astrophysics Data System (ADS)

    Holbrook, Neil J.; Goodwin, Ian D.; McGregor, Shayne; Molina, Ernesto; Power, Scott B.

    2011-03-01

    The connection between East Australian Current (EAC) transport variability and Australia's east coast sea level has received little treatment in the literature. This is due in part to the complex interacting physical processes operating in the coastal zone combined with the sparsity of observations available to improve our understanding of these possible connections. This study demonstrates a statistically significant (at the >90% level) relationship between interannual to decadal time scale variations in observed estimates of the EAC transport changes and east coast sea level measured at the high-quality, long record Fort Denison tide-gauge in Sydney Harbour, Australia (33°51'18″S, 151°13'32″E). We further demonstrate, using a linear reduced-gravity ocean model, that ENSO to decadal time-scale variations and the ocean-adjusted multi-decadal trend (approx. 1 cm/decade) in observed sea level at Fort Denison are strongly connected to modulations of EAC transports by incoming westward propagating oceanic Rossby waves. We show that EAC transport and Fort Denison sea level vary in a manner expected from both Tasman Sea generated Rossby waves, which account for the interannual and multi-annual variability, and remotely forced (from east of New Zealand) Rossby wave connections through the mid-latitudes, accounting for the ocean-adjusted multi-decadal trend observed at the New South Wales coast - with the regional-Tasman Sea forcing explaining the greatest overall proportion of EAC transport and sea-level variances.

  15. 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.

  16. 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.

  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. Determination of the Contamination Rate and the Associated Error for Targets Observed by CoRoT in the Exoplanet Channel

    NASA Astrophysics Data System (ADS)

    Gardes, B.; Chabaud, P.-Y.; Guterman, P.

    2012-09-01

    In the CoRoT exoplanet field of view, photometric measurements are obtained by aperture integration using a generic collection of masks. The total flux held within the photometric mask may be split in two parts, the target flux itself and the flux due to the nearest neighbours considered as contaminants. So far ExoDat (http://cesam.oamp.fr/exodat) gives a rough estimate of the contamination rate for all potential exoplanet targets (level-0) based on generic PSF shapes built before CoRoT launch. Here, we present the updated estimate of the contamination rate (level-1) with its associated error. This estimate is done for each target observed by CoRoT in the exoplanet channel using a new catalog of PSF built from the first available flight images and taking into account the line of sight of the satellite (i.e. the satellite orientation).

  19. Theoretical values of convective turnover times and Rossby numbers for solar-like, pre-main sequence stars

    NASA Astrophysics Data System (ADS)

    Landin, N. R.; Mendes, L. T. S.; Vaz, L. P. R.

    2010-02-01

    Context. Magnetic fields are at the heart of the observed stellar activity in late-type stars, and they are presumably generated by a dynamo mechanism at the interface layer (tachocline) between the radiative core and the base of the convective envelope. Aims: Since dynamo models are based on the interaction between differential rotation and convective motions, the introduction of rotation in the ATON 2.3 stellar evolutionary code allows for explorations regarding a physically consistent treatment of magnetic effects in stellar structure and evolution, even though there are formidable mathematical and numerical challenges involved. Methods: As examples of such explorations, we present theoretical estimates for both the local convective turnover time (τ_c), and global convective times (τ_g) for rotating pre-main sequence solar-type stars, based on up-to-date input physics for stellar models. Our theoretical predictions are compared with the previous ones available in the literature. In addition, we investigate the dependence of the convective turnover time on convection regimes, the presence of rotation and atmospheric treatment. Results: Those estimates, as opposed to the use of empirically derived values of τ_c for such matters, can be used to calculate the Rossby number Ro, which is related to the magnetic activity strength in dynamo theories and, at least for main-sequence stars, shows an observational correlation with stellar activity. More important, they can also contribute for testing stellar models against observations. Conclusions: Our theoretical values of τ_c, τ_g and Ro qualitatively agree with those published by Kim & Demarque (1996, ApJ, 457, 340). By increasing the convection efficiency, τ_g decreases for a given mass. FST models show still lower values. The presence of rotation shifts τ_g towards slightly higher values when compared with non-rotating models. The use of non-gray boundary conditions in the models yields values of τ_g smaller

  20. 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).

  1. Transiting exoplanets from the CoRoT space mission. IX. CoRoT-6b: a transiting ``hot Jupiter'' planet in an 8.9d orbit around a low-metallicity star

    NASA Astrophysics Data System (ADS)

    Fridlund, M.; Hébrard, G.; Alonso, R.; Deleuil, M.; Gandolfi, D.; Gillon, M.; Bruntt, H.; Alapini, A.; Csizmadia, Sz.; Guillot, T.; Lammer, H.; Aigrain, S.; Almenara, J. M.; Auvergne, M.; Baglin, A.; Barge, P.; Bordé, P.; Bouchy, F.; Cabrera, J.; Carone, L.; Carpano, S.; Deeg, H. J.; de La Reza, R.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Guenther, E.; Gondoin, P.; den Hartog, R.; Hatzes, A.; Jorda, L.; Léger, A.; Llebaria, A.; Magain, P.; Mazeh, T.; Moutou, C.; Ollivier, M.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Samuel, B.; Schneider, J.; Shporer, A.; Stecklum, B.; Tingley, B.; Weingrill, J.; Wuchterl, G.

    2010-03-01

    The CoRoT satellite exoplanetary team announces its sixth transiting planet in this paper. We describe and discuss the satellite observations as well as the complementary ground-based observations - photometric and spectroscopic - carried out to assess the planetary nature of the object and determine its specific physical parameters. The discovery reported here is a “hot Jupiter” planet in an 8.9d orbit, 18 stellar radii, or 0.08 AU, away from its primary star, which is a solar-type star (F9V) with an estimated age of 3.0 Gyr. The planet mass is close to 3 times that of Jupiter. The star has a metallicity of 0.2 dex lower than the Sun, and a relatively high 7Li abundance. While the light curve indicates a much higher level of activity than, e.g., the Sun, there is no sign of activity spectroscopically in e.g., the [Ca ii] H&K lines. The CoRoT space mission, launched on December 27, 2006, has been developed and is being operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA, The Research and Scientific Support Department of ESA, Germany and Spain.

  2. 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

  3. Forecasting the Dst index during corotating interaction region events using synthesized solar wind parameters

    NASA Astrophysics Data System (ADS)

    Andriyas, T.; Spencer, E.; Raj, A.; Sojka, J.; Mays, M. L.

    2012-03-01

    Observations from SOHO, STEREO, and ACE during the declining phase of the solar cycle toward the deep minimum in 2008 are analyzed to establish the timing of corotating interaction region (CIR) activity. This analysis is then employed to synthesize signals of the z component of the interplanetary magnetic field (IMF) Bz, solar wind radial velocity vx, and solar wind proton density Np at 1 AU. The synthesized signals are used as a substitute for ACE measurements to represent solar wind forcing due to coronal hole driven CIR events occurring during multiple Bartel rotations (BR 2381 to BR 2393). The signals drive a low-order physics-based model of the magnetosphere called WINDMI, one of whose outputs is the ground-based measurement of the Dst index. Estimating the arrival of CIR events for future rotations using ACE and SOHO data during BR 2381 produced what we refer to as an uncalibrated yearly forecast. We next generated a video-calibrated estimate of the arrival times of CIR events in addition to information from BR 2381 using SOHO and STEREO images of the Sun in order to produce a simulated 3.5 day ahead forecast of possible geomagnetic activity. The time of arrival of CIR events is taken to be the travel time of density compressions as seen in a noninertial frame according to a radial solar wind speed of 500 km/s and a distance of 1 AU. We were able to forecast the timing of CIR-induced geomagnetic activity to within 12 h for 17 out of 28 events by using the expected recurrence of the events through multiple Bartel rotations together with SOHO and STEREO coronal hole sightings made 3.5 days before every event. The uncertainty in the IMF Bz led to a forecast of levels of geomagnetic activity on an ensemble basis, yielding a distribution of different possible Dst signatures. We used a 10-sample ensemble and a 50-sample ensemble to obtain typical representations of geomagnetic activity. Depending on the periodicity and intensity of fluctuations in Bz, we obtained

  4. 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

  5. Examination of North-South symmetry in Saturn's sub-corotating Magnetosphere: Cassini

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    We previously investigated Saturn's sub-corotating mass-loaded spiraling magnetosphere using observations of Bφ (the azimuthal magnetic field component) in14 identical Cassini orbits near midnight in the Southern hemisphere from 0° to -80 °latitude . The basic equation representing the Magnetospheric- Ionospheric- Interaction (M-I-A), developed by Hill (1979) for Jupiter and modified by Cowley and Bunce (2002) for Saturn, is: Ip = Σp (1- ω/Ωs). Ip is the Ionospheric Pedersen Current; G is obtained from ionospheric radius, Ri, colatitude, θi, and the planetary magnetic field, Bs; Σp is altitude-integrated Pedersen conductivity; ω and Ωs are the angular rotation rates of the magnetospheric field and of Saturn Kilometric Radiation, a proxy for the planetary field rotation. The relation should hold irrespective of how the mass originates an important consideration since plasma injections are frequently imposed on radial outflow from the inner magnetosphere and used to obtain ω. Ampere's law relates Ip (Ri, θi) to Bφ (r, θ, radial distance and colatitude). It has been found that I/G = A exp(-Bθi), an exponential dependence that was not predicted, and implies that A= Σp while the exponential yields (1- ω/Ωs) so ω(θi) is determined. The derived values of ω yield a quasi-linear function of equatorial distance or L. (This dependence and an alternative expression for Ip/G also imply that ionospheric neutrals rotate at the same rate as Bs). Σp varies between 7.5 and 1.1 mho and ω(L) also varies significantly orbit-to-orbit. These are temporal variations since the orbits are spatially identical. ω(L) has been compared with ω(L) in publications based on azimuthal rotation velocity, Vφ. Hill(1979) is used to study M*, the rate of mass outflow. The general approach above has now been applied to the Northern hemisphere and the same 14 orbits. We report on the important issue of North-South symmetries and asymmetries. .

  6. The Solar Wind and Geomagnetic Activity as a Function of Time Relative to Corotating Interaction Regions

    NASA Technical Reports Server (NTRS)

    McPherron, Robert L.; Weygand, James

    2006-01-01

    Corotating interaction regions during the declining phase of the solar cycle are the cause of recurrent geomagnetic storms and are responsible for the generation of high fluxes of relativistic electrons. These regions are produced by the collision of a high-speed stream of solar wind with a slow-speed stream. The interface between the two streams is easily identified with plasma and field data from a solar wind monitor upstream of the Earth. The properties of the solar wind and interplanetary magnetic field are systematic functions of time relative to the stream interface. Consequently the coupling of the solar wind to the Earth's magnetosphere produces a predictable sequence of events. Because the streams persist for many solar rotations it should be possible to use terrestrial observations of past magnetic activity to predict future activity. Also the high-speed streams are produced by large unipolar magnetic regions on the Sun so that empirical models can be used to predict the velocity profile of a stream expected at the Earth. In either case knowledge of the statistical properties of the solar wind and geomagnetic activity as a function of time relative to a stream interface provides the basis for medium term forecasting of geomagnetic activity. In this report we use lists of stream interfaces identified in solar wind data during the years 1995 and 2004 to develop probability distribution functions for a variety of different variables as a function of time relative to the interface. The results are presented as temporal profiles of the quartiles of the cumulative probability distributions of these variables. We demonstrate that the storms produced by these interaction regions are generally very weak. Despite this the fluxes of relativistic electrons produced during those storms are the highest seen in the solar cycle. We attribute this to the specific sequence of events produced by the organization of the solar wind relative to the stream interfaces. We also

  7. The Solar Wind and Geomagnetic Activity as a Function of Time Relative to Corotating Interaction Regions

    NASA Technical Reports Server (NTRS)

    McPherron, Robert L.; Weygand, James

    2006-01-01

    Corotating interaction regions during the declining phase of the solar cycle are the cause of recurrent geomagnetic storms and are responsible for the generation of high fluxes of relativistic electrons. These regions are produced by the collision of a high-speed stream of solar wind with a slow-speed stream. The interface between the two streams is easily identified with plasma and field data from a solar wind monitor upstream of the Earth. The properties of the solar wind and interplanetary magnetic field are systematic functions of time relative to the stream interface. Consequently the coupling of the solar wind to the Earth's magnetosphere produces a predictable sequence of events. Because the streams persist for many solar rotations it should be possible to use terrestrial observations of past magnetic activity to predict future activity. Also the high-speed streams are produced by large unipolar magnetic regions on the Sun so that empirical models can be used to predict the velocity profile of a stream expected at the Earth. In either case knowledge of the statistical properties of the solar wind and geomagnetic activity as a function of time relative to a stream interface provides the basis for medium term forecasting of geomagnetic activity. In this report we use lists of stream interfaces identified in solar wind data during the years 1995 and 2004 to develop probability distribution functions for a variety of different variables as a function of time relative to the interface. The results are presented as temporal profiles of the quartiles of the cumulative probability distributions of these variables. We demonstrate that the storms produced by these interaction regions are generally very weak. Despite this the fluxes of relativistic electrons produced during those storms are the highest seen in the solar cycle. We attribute this to the specific sequence of events produced by the organization of the solar wind relative to the stream interfaces. We also

  8. Radar absorption due to a corotating interaction region encounter with Mars detected by MARSIS

    NASA Astrophysics Data System (ADS)

    Morgan, David D.; Gurnett, Donald A.; Kirchner, Donald L.; David Winningham, J.; Frahm, Rudy A.; Brain, David A.; Mitchell, David L.; Luhmann, Janet G.; Nielsen, Erling; Espley, Jared R.; Acuña, Mario H.; Plaut, Jeffrey J.

    2010-03-01

    Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is a subsurface and topside ionosphere radar sounder aboard the European Space Agency spacecraft Mars Express, in orbit at Mars since 25 December 2003, and in operation since 17 June 2005. The ionospheric sounding mode of MARSIS is capable of detecting the reflection of the sounding wave from the martian surface. This ability has been used in previous work to show that the surface reflection is absorbed and disappears during periods when high fluxes of energetic particles are incident on the ionosphere of Mars. These absorption events are believed to be the result of increased collisional damping of the sounding wave, caused by increased electron density below the spacecraft, in turn caused by impact ionization from the impinging particles. In this work we identify two absorption events that were isolated during periods when the surface reflection is consistently visible and when Mars is nearly at opposition. The visibility of the surface reflection is viewed in conjunction with particle and photon measurements taken at both Mars and Earth. Both absorption events are found to coincide with Earth passing through solar wind speed and ion flux signatures indicative of a corotating interaction region (CIR). The two events are separated by an interval of approximately 27 days, corresponding to one solar rotation. The first of the two events coincides with abruptly enhanced particle fluxes seen in situ at Mars. Simultaneous with the particle enhancement there are an abrupt decrease in the intensity of electron oscillations, typically seen by the Mars Express particle instrument ASPERA-3 between the magnetic pileup boundary and the martian bow shock, and a sharp drop in the solar wind pressure, seen in the proxy quantity based on MGS magnetometer observations. The decrease in oscillation intensity is therefore the probable effect of a relaxation of the martian bow shock. The second absorption event does

  9. A search for tight hierarchical triple systems amongst the eclipsing binaries in the CoRoT fields

    NASA Astrophysics Data System (ADS)

    Hajdu, T.; Borkovits, T.; Forgács-Dajka, E.; Sztakovics, J.; Marschalkó, G.; Benkő, J. M.; Klagyivik, P.; Sallai, M. J.

    2017-10-01

    We report a comprehensive search for hierarchical triple stellar system candidates amongst eclipsing binaries (EBs) observed by the CoRoT spacecraft. We calculate and check eclipse timing variation (ETV) diagrams for almost 1500 EBs in an automated manner. We identify five relatively short period Algol systems for which our combined light-curve and complex ETV analyses (including both the light-travel time effect and short-term dynamical third-body perturbations) resulted in consistent third-body solutions. The computed periods of the outer bodies are between 82 and 272 d (with an alternative solution of 831 d for one of the targets). We find that the inner and outer orbits are near coplanar in all but one case. The dynamical masses of the outer subsystems determined from the ETV analyses are consistent with both the results of our light-curve analyses and the spectroscopic information available in the literature. One of our candidate systems exhibits outer eclipsing events as well, the locations of which are in good agreement with the ETV solution. We also report another certain triply eclipsing triple system that, however, is lacking a reliable ETV solution due to the very short time range of the data, and four new blended systems (composite light curves of two EBs each), where we cannot decide whether the components are gravitationally bounded or not. Amongst these blended systems, we identify the longest period and highest eccentricity EB in the entire CoRoT sample.

  10. 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.

  11. 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.)

  12. Pulsation spectrum of δ Scuti stars: the binary HD 50870 as seen with CoRoT and HARPS

    NASA Astrophysics Data System (ADS)

    Mantegazza, L.; Poretti, E.; Michel, E.; Rainer, M.; Baudin, F.; García Hernández, A.; Semaan, T.; Alvarez, M.; Amado, P. J.; Garrido, R.; Mathias, P.; Moya, A.; Suárez, J. C.; Auvergne, M.; Baglin, A.; Catala, C.; Samadi, R.

    2012-06-01

    Aims: We present the results obtained with the CoRoT satellite for HD 50870, a δ Sct star which was observed for 114.4 d. The aim of these observations was to evaluate the results obtained for HD 50844, the first δ Sct star monitored with CoRoT, on a longer time baseline. Methods: The 307,570 CoRoT datapoints were analysed with different techniques. The photometric observations were complemented over 15 nights of high-resolution spectroscopy with HARPS on a baseline of 25 d. These spectra were analysed to study the line profile variations and to derive the stellar physical parameters. Some uvby photometric observations were also obtained to better characterize the pulsation modes. Results: HD 50870 proved to be a low-amplitude, long-period spectroscopic binary system seen almost pole-on (i ≃ 21°). The brighter component, which also has the higher rotational velocity (vsini = 37.5 km s-1), is a δ Sct-type variable with a full light amplitude variation of about 0.04 mag. There is a dominant axisymmetric mode (17.16 d-1). Moreover, there are two groups of frequencies (about 19) in the intervals 6 - 9 and 13 - 18 d-1, with amplitudes ranging from a few mmag to 0.3 mmag. After the detection of about 250 terms (corresponding to an amplitude of about 0.045 mmag) a flat plateau appears in the power spectrum in the low-frequency region up to about 35 d-1. We were able to detect this plateau only thanks to the short cadence sampling of the CoRoT measurements (32 s). The density distribution vs. frequency of the detected frequencies seems to rule out the possibility that this plateau is the result of a process with a continuum power spectrum. The spacings of the strongest modes suggest a quasi-periodic pattern. We failed to find a satisfactory seismic model that simultaneously matches the frequency range, the position in the HR diagram, and the quasi-periodic pattern interpreted as a large separation. Nineteen modes were detected spectroscopically from the line profile

  13. 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

  14. Capture into Mean-Motion Resonances for Exoplanetary Systems

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Many bodies in the Solar System and some exo-planets are close to or captured in Mean Motion Resonances (MMR).Capture into such resonances has been investigated by many authors. Indeed, the Hamiltonian equations of motion in presence of migration are given by Sicardy and Dubois Cel. Mech. & Dyn. Astron. , 86, 321-350 (2003). Fleming and Hamilton, Icarus 148, 479-493 (2000), studied the problem in a less generic context.In these two papers, the authors studied the problem of 1:1 corotation (Lagrange points L4 and L5), rather than m+1:m corotations (El Moutamid et al, Cel. Mech. & Dyn. Astron, 118, 235-252 (2014)).We will present a generic way to analyze details of a successful (or not) capture in the case of an oblate (or not) central body in the context of Restricted Three Body Problem (RTBP) and a more General Three Body Problem in the context of known statistics for captured exoplanets (candidates) observed by Kepler.

  15. RESONANT STRUCTURE IN THE DISKS OF SPIRAL GALAXIES, USING PHASE REVERSALS IN STREAMING MOTIONS FROM TWO-DIMENSIONAL H{alpha} FABRY-PEROT SPECTROSCOPY

    SciTech Connect

    Font, Joan; Beckman, John E.; Fathi, Kambiz; Gutierrez, Leonel; Hernandez, Olivier E-mail: jeb@iac.es E-mail: kambiz@astro.su.se E-mail: hernandez@astro.umontreal.ca

    2011-11-01

    In this Letter, we introduce a technique for finding resonance radii in a disk galaxy. We use a two-dimensional velocity field in H{alpha} emission obtained with Fabry-Perot interferometry, derive the classical rotation curve, and subtract it off, leaving a residual velocity map. As the streaming motions should reverse sign at corotation, we detect these reversals and plot them in a histogram against galactocentric radius, excluding points where the amplitude of the reversal is smaller than the measurement uncertainty. The histograms show well-defined peaks which we assume to occur at resonance radii, identifying corotations as the most prominent peaks corresponding to the relevant morphological features of the galaxy (notably bars and spiral arm systems). We compare our results with published measurements on the same galaxies using other methods and different types of data.

  16. 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

  17. Atypical energetic particle events observed prior energetic particle enhancements associated with corotating interaction regions

    NASA Astrophysics Data System (ADS)

    Khabarova, Olga; Malandraki, Olga; Zank, Gary; Jackson, Bernard; Bisi, Mario; Desai, Mihir; Li, Gang; le Roux, Jakobus; Yu, Hsiu-Shan

    2017-04-01

    Recent studies of mechanisms of particle acceleration in the heliosphere have revealed the importance of the comprehensive analysis of stream-stream interactions as well as the heliospheric current sheet (HCS) - stream interactions that often occur in the solar wind, producing huge magnetic cavities bounded by strong current sheets. Such cavities are usually filled with small-scale magnetic islands that trap and re-accelerate energetic particles (Zank et al. ApJ, 2014, 2015; le Roux et al. ApJ, 2015, 2016; Khabarova et al. ApJ, 2015, 2016). Crossings of these regions are associated with unusual variations in the energetic particle flux up to several MeV/nuc near the Earth's orbit. These energetic particle flux enhancements called "atypical energetic particle events" (AEPEs) are not associated with standard mechanisms of particle acceleration. The analysis of multi-spacecraft measurements of energetic particle flux, plasma and the interplanetary magnetic field shows that AEPEs have a local origin as they are observed by different spacecraft with a time delay corresponding to the solar wind propagation from one spacecraft to another, which is a signature of local particle acceleration in the region embedded in expanding and rotating background solar wind. AEPEs are often observed before the arrival of corotating interaction regions (CIRs) or stream interaction regions (SIRs) to the Earth's orbit. When fast solar wind streams catch up with slow solar wind, SIRs of compressed heated plasma or more regular CIRs are created at the leading edge of the high-speed stream. Since coronal holes are often long-lived structures, the same CIR re-appears often for several consecutive solar rotations. At low heliographic latitudes, such CIRs are typically bounded by forward and reverse waves on their leading and trailing edges, respectively, that steepen into shocks at heliocentric distances beyond 1 AU. Energetic ion increases have been frequently observed in association with CIR

  18. An analysis of the CoRoT-2 system: a young spotted star and its inflated giant planet

    NASA Astrophysics Data System (ADS)

    Guillot, T.; Havel, M.

    2011-03-01

    Context. CoRoT-2b is one of the most anomalously large exoplanet known. Given its high mass, its large radius cannot be explained by standard evolution models. Interestingly, the planet's parent star is an active, rapidly rotating solar-like star with with spots covering a large fraction (7-20%) of its visible surface. Aims: We attempt to constrain the properties of the star-planet system and understand whether the planet's inferred large size may be caused a systematic error in the inferred parameters, and if not, how it can be explained. Methods: We combine stellar and planetary evolution codes based on all available spectroscopic and photometric data to obtain self-consistent constraints on the system parameters. Results: We find no systematic error in the stellar modeling (including spots and stellar activity) that would cause a ~10% reduction in size of the star and thus the planet. Two classes of solutions are found: the usual main-sequence solution for the star yields for the planet a mass of 3.67 ± 0.13 MJ, a radius of 1.55 ± 0.03 RJ for an age that is at least 130 Ma and should be younger than 500 Ma given the star's rapid rotation and significant activity. We identify another class of solutions on the pre-main sequence, for which the planet's mass is 3.45 ± 0.27 MJ and its radius is 1.50 ± 0.06 RJ for an age of 30 to 40 Ma. These extremely young solutions provide the simplest explanation of the planet's size that can then be matched by a simple contraction from an initially hot, expanded state, if the atmospheric opacities are larger by a factor of ~3 than usually assumed for solar composition atmospheres. Other solutions imply that the present inflated radius of CoRoT-2b is transient and the result of an event that occurred less than 20 Ma ago, i.e., a giant impact with another Jupiter-mass planet, or interactions with another object in the system that caused a significant rise in the eccentricity followed by the rapid circularization of its orbit

  19. 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.

  20. Spectral estimates of the first few Rossby wave baroclinic modes in the South Pacific Ocean from satellite altimeters and testing of theories against these observations

    NASA Astrophysics Data System (ADS)

    Maharaj, A. M.; Cipollini, P.; Holbrook, N. J.; Killworth, P. D.; Blundell, J. R.

    2007-12-01

    Previous literature has suggested that multiple peaks in sea level anomalies (SLA) detected by two-dimensional Fourier transform (2D-FT) analysis are spectral components of multiple propagating signals which may correspond to different baroclinic Rossby wave modes. We test this hypothesis in the South Pacific Ocean by applying a 2D-FT analysis to the long Rossby wave signal determined from filtered TOPEX/Poseidon and ERS- 1/2 satellite altimeter derived SLA. The first four baroclinic mode dispersion curves for the classical linear wave theory and the Killworth and Blundell extended theory are used to determine the spectral signature and energy contributions of each mode. South of 17°S, the first two extended theory modes explain up to 60% more of the variance in the observed power spectral energy than their classical linear theory counterparts. The second mode contributes significantly over most of the basin. The third mode is also evident in some localised regions of the South Pacific but may be ignored at the large scale. Examination of a selection of case study sites suggest that bathymetric effects may dominate at longer wavelengths, or permit higher order mode solutions but mean flow tends to be the more influential factor in the extended theory. This study also examines the prevalence and characteristics of multiple propagating signals in the South Pacific SLA using the two-dimensional Radon Transform (2D-RT). Primary Radon Transform (RT) and Fourier Transform (FT) peaks generally compared well to each other and to the extended theory first baroclinic mode for most of the domain. A comparison to the energy ratios for the first four FT baroclinic modes showed that while the number of modes in their FT and peaks in the RT analysis coincided, the actual spatial distribution and relative contribution of these was not as consistent. Strong similarities existed in the spatial location and energy contribution between RT peaks 1 and 2 and FT modes 1 and 2. We

  1. 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.

  2. CoRoT measures solar-like oscillations and granulation in stars hotter than the Sun.

    PubMed

    Michel, Eric; Baglin, Annie; Auvergne, Michel; Catala, Claude; Samadi, Reza; Baudin, Frédéric; Appourchaux, Thierry; Barban, Caroline; Weiss, Werner W; Berthomieu, Gabrielle; Boumier, Patrick; Dupret, Marc-Antoine; Garcia, Rafael A; Fridlund, Malcolm; Garrido, Rafael; Goupil, Marie-Jo; Kjeldsen, Hans; Lebreton, Yveline; Mosser, Benoît; Grotsch-Noels, Arlette; Janot-Pacheco, Eduardo; Provost, Janine; Roxburgh, Ian W; Thoul, Anne; Toutain, Thierry; Tiphène, Didier; Turck-Chieze, Sylvaine; Vauclair, Sylvie D; Vauclair, Gérard P; Aerts, Conny; Alecian, Georges; Ballot, Jérôme; Charpinet, Stéphane; Hubert, Anne-Marie; Lignières, François; Mathias, Philippe; Monteiro, Mario J P F G; Neiner, Coralie; Poretti, Ennio; de Medeiros, José Renan; Ribas, Ignasi; Rieutord, Michel L; Cortés, Teodoro Roca; Zwintz, Konstanze

    2008-10-24

    Oscillations of the Sun have been used to understand its interior structure. The extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the international community over the past decades. The CoRoT (Convection Rotation and Planetary Transits) satellite, launched in December 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. The oscillation amplitudes are about 1.5 times as large as those in the Sun; the stellar granulation is up to three times as high. The stellar amplitudes are about 25% below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.

  3. The ESA-ANISAP Study: Retrieval Of Tropospheric Water Vapour Fields By Using Co-Rotating LEO Satellites

    NASA Astrophysics Data System (ADS)

    Argenti, F.; Facheris, L.; Cuccoli, F.; Lapini, A.

    2013-12-01

    This paper presents a preliminary study for the estimation of 2-D maps of atmospheric water vapour content from integrated water vapour measurements carried out by a constellation of co-rotating low earth orbit satellites. The proposed method uses the normalised differential spectral attenuation (NDSA) approachable to achieve integrated water vapour content information from attenuations measurements over microwave links among the satellites - and tomographic techniques to solve the inverse problem of atmospheric water vapour field reconstruction. This study is undertaken as a task of the on-going research developed under the ESA-ANISAP project. Some simulation results demonstrating the feasibility of the reconstruction of 2-D maps of atmospheric water vapour content are presented.

  4. Dissecting the Multi-Component Nature of NGC 7217 with VIRUS-W: Two Co-Rotating Stellar Components

    NASA Astrophysics Data System (ADS)

    Fabricius, M. H.; Coccato, L.; Bender, R.; Drory, N.; Saglia, R. P.; Williams, M.; Landriau, M.

    2014-05-01

    Previous studies have reported the existence of two counter rotating stellar disks in the early type spiral galaxy NGC 7217. We have obtained optical high resolution (R≃9000) spectroscopic data with the new fiber-based integral-field unit instrument VIRUS-W at the 2.7-m telescope of the McDonald Observatory in Texas. Our analysis confirms the existence of two components. We find them however to be co-rotating. Their vastly different velocity dispersions (˜ 20 km s-1 vs. ˜ 170 km s-1) allow us to perform a kinematic decomposition and to measure abundances in the two components. Our data suggest that NGC 7217 may be in the process of (re)growing a disk inside a more massive and higher velocity dispersion stellar bulge.

  5. Ultra-precise analysis of the light curves of CoRoT and Kepler δ Scuti stars

    NASA Astrophysics Data System (ADS)

    Pascual-Granado, Javier; Suárez, Juan Carlos; Garrido, Rafael

    2017-09-01

    It is well known that the residuals of the multifrequency analysis of δ Scuti stars are correlated, giving rise to challenging features such as a plateau (HD 50844, HD 50870, HD 49434, …) of non-resolved frequencies with amplitude higher than the expected noise level. Several hypotheses have been advanced to explain these features: effective convection, rotation, non-linear interactions, etc. We have recently demonstrated that in some cases the underlying function describing the light variations of δ Scuti stars has not the property of being analytic. The strong consequence of this result is that the Fourier expansion on which the harmonic analysis is based could be not justified. In order to know the extension of this phenomenon among δ Scuti stars, we have used photometric data from CoRoT seismofield and a set of Kepler stars. The results show that this inconsistency in the application of harmonic analysis is almost ubiquitous to the δ Scuti pulsating stars.

  6. 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).

  7. 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

  8. Experimental observation of self excited co-rotating multiple vortices in a dusty plasma with inhomogeneous plasma background

    NASA Astrophysics Data System (ADS)

    Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

    2017-03-01

    We report an experimental observation of multiple co-rotating vortices in an extended dust column in the background of an inhomogeneous diffused plasma. An inductively coupled rf discharge is initiated in the background of argon gas in the source region. This plasma was later found to diffuse into the main experimental chamber. A secondary DC glow discharge plasma is produced to introduce dust particles into the plasma volume. These micron-sized poly-disperse dust particles get charged in the background of the DC plasma and are transported by the ambipolar electric field of the diffused plasma. These transported particles are found to be confined in an electrostatic potential well, where the resultant electric field due to the diffused plasma (ambipolar E-field) and glass wall charging (sheath E-field) holds the micron-sized particles against the gravity. Multiple co-rotating (anti-clockwise) dust vortices are observed in the dust cloud for a particular discharge condition. The transition from multiple vortices to a single dust vortex is observed when input rf power is lowered. The occurrence of these vortices is explained on the basis of the charge gradient of dust particles, which is orthogonal to the ion drag force. The charge gradient is a consequence of the plasma inhomogeneity along the dust cloud length. The detailed nature and the reason for multiple vortices are still under investigation through further experiments; however, preliminary qualitative understanding is discussed based on the characteristic scale length of the dust vortex. There is a characteristic size of the vortex in the dusty plasma; therefore, multiple vortices could possibly be formed in an extended dusty plasma with inhomogeneous plasma background. The experimental results on the vortex motion of particles are compared with a theoretical model and are found to be in close agreement.

  9. 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.

  10. Forced resonant undulation in the deep Mascarene Basin

    NASA Astrophysics Data System (ADS)

    Warren, Bruce A.; Whitworth, Thomas; LaCasce, Joseph H.

    Current meters moored for 19.5 months at Lat. 20°S in the deep water of the western Mascarene Basin recorded a distinct, large-amplitude [O(10 cm s -1)] undulation of bimonthly period, propagating westward at 7 cm s -1. Its characteristics demonstrate that it was a barotropic Rossby wave of relatively large meridional scale. Simple theory accounts for it as having been forced by local wind-stress curl at one of the resonant frequencies of the Mascarene Basin. A sharp bimonthly peak is also prominent in spectra of TOPEX/POSEIDON sea-surface height in the Mascarene Basin, but is not seen to the eastward, as is consistent with the local generation. Fluctuations of 45-day period reported earlier in the upper ocean just northeast of Madagascar might have been generated through a similar process, but with frequency shifted by the South Equatorial Current.

  11. 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.

  12. 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.

    2016-12-01

    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.

  13. 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

  14. Snake resonances

    SciTech Connect

    Tepikian, S.

    1988-01-01

    Siberian Snakes provide a practical means of obtaining polarized proton beams in large accelerators. The effect of snakes can be understood by studying the dynamics of spin precession in an accelerator with snakes and a single spin resonance. This leads to a new class of energy independent spin depolarizing resonances, called snake resonances. In designing a large accelerator with snakes to preserve the spin polarization, there is an added constraint on the choice of the vertical betatron tune due to the snake resonances. 11 refs., 4 figs.

  15. YSOVAR II: Mapping YSO Inner Disk Structure in NGC 2264 with Simultaneous Spitzer and CoRoT Time Series Photometry

    NASA Astrophysics Data System (ADS)

    Stauffer, John; Morales-Calderon, Maria; Rebull, Luisa; Affer, Laura; Alencar, Sylvia; Allen, Lori; Barrado, David; Bouvier, Jerome; Calvet, Nuria; Carey, Sean; Carpenter, John; Ciardi, David; Covey, Kevin; D'Alessio, Paola; Espaillat, Catherine; Favata, Fabio; Flaccomio, Ettore; Forbrich, Jan; Furesz, Gabor; Hartman, Lee; Herbst, William; Hillenbrand, Lynne; Holtzman, Jon; Hora, Joe; Marchis, Franck; McCaughrean, Mark; Micela, Giusi; Mundt, Reinhard; Plavchan, Peter; Turner, Neal; Skrutzkie, Mike; Smith, Howard; Song, Inseok; Szentgyorgi, Andy; Terebey, Susan; Vrba, Fred; Wasserman, Lawrence; Watson, Alan; Whitney, Barbara; Winston, Elaine; Wood, Kenny

    2011-05-01

    We propose a simultaneous, continuous 30 day observation of the star forming region NGC2264 with Spitzer and CoRoT. NGC2264 is the only nearby, rich star-forming region which can be observed with CoRoT; it is by definition then the only nearby, rich star-forming region where a simultaneous Spitzer/CoRoT campaign is possible. Fortunately, the visibility windows for the two spacecraft overlap, allowing this program to be done in the Nov. 25, 2011 to Jan. 4, 2012 time period. For 10 days, we propose to map the majority of the cluster (a 35'x35' region) to a depth of 48 seconds per point, with each epoch taking 1.7 hours, allowing of order 12 epochs per day. For the other 20 days, we propose to obtaining staring-mode data for two positions in the cluster having a high density of cluster members. We also plan to propose for a variety of other ground and space-based data, most of which would also be simultaneous with the Spitzer and CoRoT observing. These data will allow us to address many astrophysical questions related to the structure and evolution of the disks of young stars and the interaction of those disks with the forming star. The data may also help inform models of planet formation since planets form and migrate through the pre-main sequence disks during the 0.5-5 Myr age range of stars in NGC2264. The data we collect will also provide an archive of the variability properties of young stars that is unmatched in its accuracy, sensitivity, cadence and duration and which therefore could inspire investigation of phenomena which we cannot now imagine. The CoRoT observations have been approved, contingent on approval of a simultaneous Spitzer observing program (this proposal).

  16. The tip of the iceberg: the frequency content of the δ Sct star HD 50844 from CoRoT space photometry

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

    It has been suggested that the detection of a wealth of very low amplitude modes in δ Sct stars was only a matter of signal-to-noise ratio. Access to this treasure, impossible from the ground, is one of the scientific aims of the space mission CoRoT, developed and operated by CNES. This work presents the results obtained on HD 50844: the 140,016 datapoints allowed us to reach the level of 10-5 mag in the amplitude spectra. The frequency analysis of the CoRoT timeseries revealed hundreds of terms in the frequency range 0-30 d-1. 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 = 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. The predominant term (f1 = 6.92 d-1) has been identified as the fundamental radial mode combining ground-based photometric and spectroscopic data.

  17. 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.

  18. On posterior probability and significance level: application to the power spectrum of HD 49 933 observed by CoRoT

    NASA Astrophysics Data System (ADS)

    Appourchaux, T.; Samadi, R.; Dupret, M.-A.

    2009-10-01

    Context: The CoRoT mission provides asteroseismic data of very high quality allowing one to adopt new statistical approaches for mode detection in power spectra, especially with respect to testing the null hypothesis (H{0}, which assumes that what is observed is pure noise). Aims: We emphasize that the significance level when rejecting the null hypothesis can lead to the incorrect conclusion that the H{0} hypothesis is unlikely to occur at that significance level. We demonstrate that the significance level is unrelated to the posterior probability of H{0}, given the observed data set, and that this posterior probability is very much higher than implied by the significance level. Methods: We use Bayes theorem to derive the posterior probability of that H{0} is true assuming an alternative hypothesis H{1} that a mode is present, taking some prior for the mode height, mode amplitude and linewidth. Results: We compute the posterior probability of H{0} for the p modes detected on HD 49 933 by CoRoT. Conclusions: We conclude that the posterior probability of H{0} provide a much more conservative quantification of the mode detection than the significance level. This framework can be applied to any similar stellar power spectra obtained to complete asteroseismology. 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.

  19. Nonlinear resonance

    NASA Astrophysics Data System (ADS)

    Kevorkian, J.

    This report discusses research in the area of slowly varying nonlinear oscillatory systems. Some of the topics discussed are as follows: adiabatic invariants and transient resonance in very slowly varying Hamiltonian systems; sustained resonance in very slowly varying Hamiltonian systems; free-electron lasers with very slow wiggler taper; and bursting oscillators.

  20. Nonlinear resonance

    NASA Astrophysics Data System (ADS)

    Kevorkian, J.; Pernarowski, Mark; Bosley, David L.

    1990-04-01

    The subjects discussed are: transient and sustained resonance for systems with very slowly varying parameters; free electron lasers with very slow wiggler taper; and bursting oscillations in biological systems. Plans are discussed for: FEL applications; transient and sustained resonance; and bursting oscillations.

  1. 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.

  2. 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.

  3. Constraining planet structure from stellar chemistry: the cases of CoRoT-7, Kepler-10, and Kepler-93

    NASA Astrophysics Data System (ADS)

    Santos, N. C.; Adibekyan, V.; Mordasini, C.; Benz, W.; Delgado-Mena, E.; Dorn, C.; Buchhave, L.; Figueira, P.; Mortier, A.; Pepe, F.; Santerne, A.; Sousa, S. G.; Udry, S.

    2015-08-01

    Aims: We explore the possibility that the stellar relative abundances of different species can be used to constrain the bulk abundances of known transiting rocky planets. Methods: We use high resolution spectra to derive stellar parameters and chemical abundances for Fe, Si, Mg, O, and C in three stars hosting low mass, rocky planets: CoRoT-7, Kepler-10, and Kepler-93. These planets follow the same line along the mass-radius diagram, pointing toward a similar composition. The derived abundance ratios are compared with the solar values. With a simple stoichiometric model, we estimate the iron mass fraction in each planet, assuming stellar composition. Results: We show that in all cases, the iron mass fraction inferred from the mass-radius relationship seems to be in good agreement with the iron abundance derived from the host star's photospheric composition. Conclusions: The results suggest that stellar abundances can be used to add constraints on the composition of orbiting rocky planets. Based on archival data obtained with the SOPHIE (1.93-m telescope OHP observatory), HARPS (3.6-m ESO, La Silla-Paranal Observatory), and HARPS-N (TNG telescope, La Palma) spectrographs.Appendices are available in electronic form at http://www.aanda.org

  4. 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).

  5. 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.

  6. 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.

  7. CoRoT 223992193: Investigating the variability in a low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk

    NASA Astrophysics Data System (ADS)

    Gillen, E.; Aigrain, S.; Terquem, C.; Bouvier, J.; Alencar, S. H. P.; Gandolfi, D.; Stauffer, J.; Cody, A.; Venuti, L.; Almeida, P. Viana; Micela, G.; Favata, F.; Deeg, H. J.

    2017-02-01

    CoRoT 223992193 is the only known low-mass, pre-main sequence eclipsing binary that shows evidence of a circumbinary disk. The system displays complex photometric and spectroscopic variability over a range of timescales and wavelengths. Using two optical CoRoT runs from 2008 and 2011/2012 (spanning 23 and 39 days), along with infrared Spitzer 3.6 and 4.5 μm observations (spanning 21 and 29 days, and simultaneous with the second CoRoT run), we model the out-of-eclipse light curves, finding that the large scale structure in both CoRoT light curves is consistent with the constructive and destructive interference of starspot signals at two slightly different periods. Using the vsini of both stars, we interpret this as the two stars having slightly different rotation periods: the primary is consistent with synchronisation and the secondary rotates slightly supersynchronously. Comparison of the raw 2011/2012 light curve data to the residuals of our spot model in colour-magnitude space indicates additional contributions consistent with a combination of variable dust emission and obscuration. There appears to be a tentative correlation between this additional variability and the binary orbital phase, with the system displaying increases in its infrared flux around primary and secondary eclipse. We also identify short-duration flux dips preceding secondary eclipse in all three CoRoT and Spitzer bands. We construct a model of the inner regions of the binary and propose that these dips could be caused by partial occultation of the central binary by the accretion stream onto the primary star. Analysis of 15 Hα profiles obtained with the FLAMES instrument on the Very Large Telescope reveal an emission profile associated with each star. The majority of this is consistent with chromospheric emission but additional higher velocity emission is also seen, which could be due to prominences. However, half of the secondary star's emission profiles display full widths at 10% intensity

  8. MIARMA: A minimal-loss information method for filling gaps in time series. Application to CoRoT light curves

    NASA Astrophysics Data System (ADS)

    Pascual-Granado, J.; Garrido, R.; Suárez, J. C.

    2015-03-01

    Context. Gaps in time series cause spurious frequencies in the power spectra. In light curves of pulsating stars, this hampers identifying the theoretical oscillation modes. When these gaps are smaller than the total time span, the commonly used approach to overcome these difficulties involves linear interpolation. The original frequency content of the pulsating stars is not preserved in the resulting time series. Aims: The method presented here intends to minimize the effect of the gaps in the power spectra by gap-filling that preserves at best the original information, that is, the stellar oscillation frequency content for asteroseismology. Methods: We used a forward-backward predictor based on autoregressive moving-average modelling (ARMA) in the time domain. The algorithm MIARMA is particularly suitable for replacing invalid data such as those present in the light curves of the CoRoT satellite due to the pass through the South Atlantic Anomaly, and eventually for the data gathered by the NASA planet hunter Kepler. We selected a sample of stars from the ultra-precise photometry collected by the asteroseismic camera on board the CoRoT satellite: the δ Scuti star HD 174966, showing periodic variations of the same order as the CoRoT observational window, the Be star HD 51193, showing longer time variations, and the solar-like HD 49933, with rapid time variations. Results: We show that in some cases linear interpolations are less reliable than previously believed. The ARMA interpolation method provides a cleaner power spectrum, that is, less contaminated by spurious frequencies. In summary, MIARMA appears to be a suitable method for filling gaps in the light curves of pulsating stars observed by CoRoT since the method aims to preserve their frequency content, which is a necessary condition for asteroseismic studies. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil

  9. Long Wave Resonance in Tropical Oceans and Implications on Climate: the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Pinault, Jean-Louis

    2013-11-01

    Based on the well established importance of long, non-dispersive baroclinic Kelvin and Rossby waves, a resonance of tropical planetary waves is demonstrated. Three main basin modes are highlighted through joint wavelet analyses of sea surface height (SSH) and surface current velocity (SCV), scale-averaged over relevant bands to address the co-variability of variables: (1) a 1-year period quasi-stationary wave (QSW) formed from gravest mode baroclinic planetary waves which consists of a northern, an equatorial and a southern antinode, and a major node off the South American coast that straddles the north equatorial current (NEC) and the north equatorial counter current (NECC), (2) a half-a-year period harmonic, (3) an 8-year sub-harmonic. Contrary to what is commonly accepted, the 1-year period QSW is not composed of wind-generated Kelvin and Rossby beams but results from the excitation of a tuned basin mode. Trade winds sustain a free tropical basin mode, the natural frequency of which is tuned to synchronize the excitation and the ridge of the QSWs. The functioning of the 1-year period basin mode is confirmed by solving the momentum equations, expanding in terms of Fourier series both the coefficients and the forcing terms. The terms of Fourier series have singularities, highlighting resonances and the relation between the resonance frequency and the wavenumbers. This ill-posed problem is regularized by considering Rayleigh friction. The waves are supposed to be semi-infinite, i.e. they do not reflect at the western and eastern boundaries of the basin, which would assume the waves vanish at these boundaries. At the western boundary the equatorial Rossby wave is deflected towards the northern antinode while forming the NECC that induces a positive Doppler-shifted wavenumber. At the eastern boundary, the Kelvin wave splits into coastal Kelvin waves that flow mainly southward to leave the Gulf of Guinea. In turn, off-tropical waves extend as an equatorially trapped

  10. Resonance Van Hove singularities in wave kinetics

    NASA Astrophysics Data System (ADS)

    Shi, Yi-Kang; Eyink, Gregory L.

    2016-10-01

    Wave kinetic theory has been developed to describe the statistical dynamics of weakly nonlinear, dispersive waves. However, we show that systems which are generally dispersive can have resonant sets of wave modes with identical group velocities, leading to a local breakdown of dispersivity. This shows up as a geometric singularity of the resonant manifold and possibly as an infinite phase measure in the collision integral. Such singularities occur widely for classical wave systems, including acoustical waves, Rossby waves, helical waves in rotating fluids, light waves in nonlinear optics and also in quantum transport, e.g. kinetics of electron-hole excitations (matter waves) in graphene. These singularities are the exact analogue of the critical points found by Van Hove in 1953 for phonon dispersion relations in crystals. The importance of these singularities in wave kinetics depends on the dimension of phase space D =(N - 2) d (d physical space dimension, N the number of waves in resonance) and the degree of degeneracy δ of the critical points. Following Van Hove, we show that non-degenerate singularities lead to finite phase measures for D > 2 but produce divergences when D ≤ 2 and possible breakdown of wave kinetics if the collision integral itself becomes too large (or even infinite). Similar divergences and possible breakdown can occur for degenerate singularities, when D - δ ≤ 2, as we find for several physical examples, including electron-hole kinetics in graphene. When the standard kinetic equation breaks down, then one must develop a new singular wave kinetics. We discuss approaches from pioneering 1971 work of Newell & Aucoin on multi-scale perturbation theory for acoustic waves and field-theoretic methods based on exact Schwinger-Dyson integral equations for the wave dynamics.

  11. Acoustic Resonators

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2012-11-01

    Recently my collection of historical physics teaching apparatus was given a group of 19th-century tuning forks on resonant boxes. Figure 1 shows the smallest fork sitting on the largest one. The large tuning fork oscillates at 128 Hz and has a resonator that is 57.9 cm long. The small fork has a frequency 10 times higher, but its resonator has a length of 11.0 cm instead of the 5.8 cm that simple scaling would suggest. How is this possible?

  12. 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.

  13. The diameter of the CoRoT target HD 49933. Combining the 3D limb darkening, asteroseismology, and interferometry

    NASA Astrophysics Data System (ADS)

    Bigot, L.; Mourard, D.; Berio, P.; Thévenin, F.; Ligi, R.; Tallon-Bosc, I.; Chesneau, O.; Delaa, O.; Nardetto, N.; Perraut, K.; Stee, Ph.; Boyajian, T.; Morel, P.; Pichon, B.; Kervella, P.; Schmider, F. X.; McAlister, H.; ten Brummelaar, T.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; Turner, N.; Farrington, C.; Goldfinger, P. J.

    2011-10-01

    Context. The interpretation of stellar pulsations in terms of internal structure depends on the knowledge of the fundamental stellar parameters. Long-base interferometers permit us to determine very accurate stellar radii, which are independent constraints for stellar models that help us to locate the star in the HR diagram. Aims: Using a direct interferometric determination of the angular diameter and advanced three-dimensional (3D) modeling, we derive the radius of the CoRoT target HD 49933 and reduce the global stellar parameter space compatible with seismic data. Methods: The VEGA/CHARA spectro-interferometer is used to measure the angular diameter of the star. A 3D radiative hydrodynamical simulation of the surface is performed to compute the limb darkening and derive a reliable diameter from visibility curves. The other fundamental stellar parameters (mass, age, and Teff) are found by fitting the large and small p-mode frequency separations using a stellar evolution model that includes microscopic diffusion. Results: We obtain a limb-darkened angular diameter of θLD = 0.445 ± 0.012 mas. With the Hipparcos parallax, we obtain a radius of R = 1.42 ± 0.04 R⊙. The corresponding stellar evolution model that fits both large and small frequency separations has a mass of 1.20 ± 0.08 M⊙ and an age of 2.7 Gy. The atmospheric parameters are Teff = 6640 ± 100 K, log g = 4.21 ± 0.14, and [Fe/H] = -0.38.

  14. Ks-band Detection of Thermal Emission and Color Constraints to the Hot Jupiter CoRoT-1b

    NASA Astrophysics Data System (ADS)

    Rogers, Justin; Apai, D.; Lopez-Morales, M.; Sing, D.; Burrows, A.; Sterzik, M.

    2010-01-01

    We report the detection in Ks-band of the secondary eclipse of the hot Jupiter CoRoT-1b, from time series photometry with the ARC 3.5-m telescope at Apache Point Observatory. The eclipse shows a depth of 0.336 +/- 0.042 percent, and is centered at a phase consistent with a circular orbit. We then perform the first optical to near-infrared multi-band photometric analysis of an exoplanet's atmosphere by combining our result with the recent 0.6, 0.71, and 2.09 micron eclipse detections by Snellen et al. (2009), Gillon et al. (2009), and Alonso et al. (2009). Comparing the multi-wavelength detections to state-of-the-art radiative-convective chemical equilibrium atmosphere models, we find the near-infrared fluxes difficult to reproduce. The best physical model suggests a thermal inversion layer with an extra optical absorber of opacity kappae = 0.05 cm2 g-1 placed near the 0.1-bar atmospheric pressure level, ten times deeper in the atmosphere than the absorbers used in models to fit mid-infrared Spitzer detections of other irradiated hot Jupiters. We also present and discuss preliminary results from secondary eclipse observations of other planets. We are grateful for the critical support provided by the Space Telescope Science Institute Director's Discretionary Research Fund D0101.90131, Hubble Fellowship grant HF-01210.01-A, CNES, NASA grant NNX07AG80G, and National Science Foundation grant AST-0908278.

  15. 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.

  16. Prospective Out-of-ecliptic White-light Imaging of Interplanetary Corotating Interaction Regions at Solar Maximum

    NASA Astrophysics Data System (ADS)

    Xiong, Ming; Davies, Jackie A.; Li, Bo; Yang, Liping; Liu, Ying D.; Xia, Lidong; Harrison, Richard A.; Keiji, Hayashi; Li, Huichao

    2017-07-01

    Interplanetary corotating interaction regions (CIRs) can be remotely imaged in white light (WL), as demonstrated by the Solar Mass Ejection Imager (SMEI) on board the Coriolis spacecraft and Heliospheric Imagers (HIs) on board the twin Solar TErrestrial RElations Observatory (STEREO) spacecraft. The interplanetary WL intensity, due to Thomson scattering of incident sunlight by free electrons, is jointly determined by the 3D distribution of electron number density and line-of-sight (LOS) weighting factors of the Thomson-scattering geometry. The 2D radiance patterns of CIRs in WL sky maps look very different from different 3D viewpoints. Because of the in-ecliptic locations of both the STEREO and Coriolis spacecraft, the longitudinal dimension of interplanetary CIRs has, up to now, always been integrated in WL imagery. To synthesize the WL radiance patterns of CIRs from an out-of-ecliptic (OOE) vantage point, we perform forward magnetohydrodynamic modeling of the 3D inner heliosphere during Carrington Rotation CR1967 at solar maximum. The mixing effects associated with viewing 3D CIRs are significantly minimized from an OOE viewpoint. Our forward modeling results demonstrate that OOE WL imaging from a latitude greater than 60° can (1) enable the garden-hose spiral morphology of CIRs to be readily resolved, (2) enable multiple coexisting CIRs to be differentiated, and (3) enable the continuous tracing of any interplanetary CIR back toward its coronal source. In particular, an OOE view in WL can reveal where nascent CIRs are formed in the extended corona and how these CIRs develop in interplanetary space. Therefore, a panoramic view from a suite of wide-field WL imagers in a solar polar orbit would be invaluable in unambiguously resolving the large-scale longitudinal structure of CIRs in the 3D inner heliosphere.

  17. Mapping the conjugate and corotating storm-enhanced density during 17 March 2013 storm through data assimilation

    NASA Astrophysics Data System (ADS)

    Yue, Xinan; Wan, Weixing; Liu, Libo; Liu, Jing; Zhang, Shunrong; Schreiner, William S.; Zhao, Biqiang; Hu, Lianhuan

    2016-12-01

    The storm-enhanced density (SED) is an electron density enhancement phenomenon extending from the later afternoon at middle latitude to the noontime in high latitude within a narrow band during early stage of geomagnetic storm. Previous investigations were mostly focused on the northern America region due to sparse data coverage in other regions. Recent observational analysis and simulation studies have shown that the SED might be quite complicated both physically and spatial/temporal evolution. In this paper, we obtained the global ionospheric electron density with the spatial/temporal resolution of 5° in latitude, 10° in longitude, 30 km around F2 peak, and 0.5 h in time, during 17 March 2013 geomagnetic storm through assimilating ground and LEO-based total electron content (TEC) data into the model. A total of 450 ground-based Global Navigation Satellite Systems stations' and 10 LEO satellites' observations were applied in the assimilation. Of all the data, six satellites with ionospheric radio occultation profiling capability provided the key altitudinal variation information. The SED associated with the tongue of ionization (TOI) and boundary blob can be well identified from the data assimilation results, although their amplitude of enhancement was only up to 6 TECU (TEC unit, 1 TECU = 1016 el m-2). All structures show very dynamic and complicated time evolution features. During this storm time, we identified two separate SED/TOI/blob structures corotating from Europe to American with conjugate occurrence. This partly supports the mechanism of convection expansion. Given a significant amount of radio occultation will be available in the near future, this method will help up us to resolve global large-scale ionospheric disturbance down to very small spatial and temporal scale in storm time.

  18. 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.

  19. 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

    2017-01-01

    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.

  20. An analysis on the generation of Rossby waves and gravity waves in the MLT region based on satellite and whole atmosphere model data

    NASA Astrophysics Data System (ADS)

    Yasui, R.; Sato, K.; Miyoshi, Y.

    2016-12-01

    In the middle atmosphere, gravity waves (GWs), tides (TWs) and Rossby waves (RWs) are dominant. By interacting with the mean flow and driving the atmospheric global circulation, these waves maintain the thermal structure which is partly much different from that expected from a radiative balance. GWs are mainly generated in the troposphere and play important roles in the mesosphere. Planetary-scale RWs are dominant in the mesosphere, which are called quasi-two day waves in the summer hemisphere or 4-day waves in the winter hemisphere. However, the momentum budget of the middle atmosphere has not thoroughly examined particularly for the mesosphere and lower thermosphere (MLT). In this study, the momentum budget in the MLT region is examined in terms of respective contribution by these waves by using a satellite data and a whole atmosphere model data. Analyzed data are the temperature and geopotential height data from Aura MLS observation as a satellite data and the neutral atmosphere data from the Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA), which is a whole atmosphere model. The analyzed period is about 11 years from 8 August 2004 to 19 June 2015. For the RW component, EPFD is significantly positive in the summer mesosphere. Strong upward EPF above the positive EPFD region is extended up to 110 km in the lower thermosphere. By potential vorticity (PV) analysis, it seems that RWs associated with this strong upward EPF are radiated from the PV maximum in the summer mesosphere. This PV maximum is caused by increase in both static stability and relative vorticity due to parameterized GW forcing in GAIA model. Interestingly, there are significant resolved GW components having strong EPF and EPFD. In the summer MLT region, eastward GWs with downward EPF are dominant particularly above the PV maximum. The frequency of Richardson number (Ri) smaller than 1/4 is higher in this region, suggesting that the GW are generated by shear instability in

  1. The Evolution of the G Ring Arc under the Effects of the Resonance with Mimas and the Solar Radiation Force

    NASA Astrophysics Data System (ADS)

    Mourão, D. C.; Giuliatti Winter, S. M.; Sfair, R.

    2014-10-01

    The small satellite Aegaeon, less than 1km across, is embedded in an arc located in the G ring of Saturn. This satellite belong to a new class of structures imaged by the Cassini spacecraft, which is formed by small satellites immersed in arcs. Aegaeon is also locked in a 7:6 corotation resonance with the satellite Mimas. It has been proposed that Aegaoen, along with a set of large particles located in this arc, is responsible for the maintenance of the G ring against dissipative forces. In this work, we study the orbital evolution of a sample of tiny particles (sizes ranging from 1 to 100m) under the gravitational effects of Mimas and the solar radiation pressure. These particles were initially spread both along the ring, about ± 20 km from the semimajor axis resonance of Aegaeon, and close to the Aegaeon's surface. Our results show that, despite the particles are initially in a corotation resonance with Mimas, the effects of the solar radiation pressure remove by collision with Aegaeon most of smallest particles from the arc in a timespan of 100yrs. The remaining particles stay confined in the G ring.

  2. Multiquark resonances

    DOE PAGES

    Esposito, A.; Pilloni, A.; Polosa, Antonio D.

    2016-12-02

    Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties have been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building.more » Lastly, data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.« less

  3. Multiquark resonances

    NASA Astrophysics Data System (ADS)

    Esposito, A.; Pilloni, A.; Polosa, A. D.

    2017-01-01

    Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties have been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building. Data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.

  4. Multiquark resonances

    SciTech Connect

    Esposito, A.; Pilloni, A.; Polosa, Antonio D.

    2016-12-02

    Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties have been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building. Lastly, data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.

  5. 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

  6. CoRoT 223992193: A new, low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk

    NASA Astrophysics Data System (ADS)

    Gillen, E.; Aigrain, S.; McQuillan, A.; Bouvier, J.; Hodgkin, S.; Alencar, S. H. P.; Terquem, C.; Southworth, J.; Gibson, N. P.; Cody, A.; Lendl, M.; Morales-Calderón, M.; Favata, F.; Stauffer, J.; Micela, G.

    2014-02-01

    We present the discovery of CoRoT 223992193, a double-lined, detached eclipsing binary, comprising two pre-main sequence M dwarfs, discovered by the CoRoT space mission during a 23-day observation of the 3 Myr old NGC 2264 star-forming region. Using multi-epoch optical and near-IR follow-up spectroscopy with FLAMES on the Very Large Telescope and ISIS on the William Herschel Telescope we obtain a full orbital solution and derive the fundamental parameters of both stars by modelling the light curve and radial velocity data. The orbit is circular and has a period of 3.8745745 ± 0.0000014 days. The masses and radii of the two stars are 0.67 ± 0.01 and 0.495 ± 0.007 M⊙ and 1.30 ± 0.04 and 1.11-0.05+0.04 R⊙, respectively. This system is a useful test of evolutionary models of young low-mass stars, as it lies in a region of parameter space where observational constraints are scarce; comparison with these models indicates an apparent age of ~3.5-6 Myr. The systemic velocity is within 1σ of the cluster value which, along with the presence of lithium absorption, strongly indicates cluster membership. The CoRoT light curve also contains large-amplitude, rapidly evolving out-of-eclipse variations, which are difficult to explain using starspots alone. The system's spectral energy distribution reveals a mid-infrared excess, which we model as thermal emission from a small amount of dust located in the inner cavity of a circumbinary disk. In turn, this opens up the possibility that some of the out-of-eclipse variability could be due to occultations of the central stars by material located at the inner edge or in the central cavity of the circumbinary disk. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESAs RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

  7. The pulsations of the B5IVe star HD 181231 observed with CoRoT and ground-based spectroscopy

    NASA Astrophysics Data System (ADS)

    Neiner, C.; Gutiérrez-Soto, J.; Baudin, F.; de Batz, B.; Frémat, Y.; Huat, A. L.; Floquet, M.; Hubert, A.-M.; Leroy, B.; Diago, P. D.; Poretti, E.; Carrier, F.; Rainer, M.; Catala, C.; Thizy, O.; Buil, C.; Ribeiro, J.; Andrade, L.; Emilio, M.; Espinosa Lara, F.; Fabregat, J.; Janot-Pacheco, E.; Martayan, C.; Semaan, T.; Suso, J.; Baglin, A.; Michel, E.; Samadi, R.

    2009-10-01

    Context: HD 181231 is a B5IVe star, which has been observed with the CoRoT satellite during ~5 consecutive months and simultaneously from the ground in spectroscopy and spectropolarimetry. Aims: By analysing these data, we aim to detect and characterize as many pulsation frequencies as possible, to search for the presence of beating effects possibly at the origin of the Be phenomenon. Our results will also provide a basis for seismic modelling. Methods: The fundamental parameters of the star are determined from spectral fitting and from the study of the circumstellar emission. The CoRoT photometric data and ground-based spectroscopy are analysed using several Fourier techniques: Clean-ng, Pasper, and Tisaft, as well as a time-frequency technique. A search for a magnetic field is performed by applying the LSD technique to the spectropolarimetric data. Results: We find that HD 181231 is a B5IVe star seen with an inclination of ~45 degrees. No magnetic field is detected in its photosphere. We detect at least 10 independent significant frequencies of variations among the 54 detected frequencies, interpreted in terms of non-radial pulsation modes and rotation. Two longer-term variations are also detected: one at ~14 days resulting from a beating effect between the two main frequencies of short-term variations, the other at ~116 days due either to a beating of frequencies or to a zonal pulsation mode. Conclusions: Our analysis of the CoRoT light curve and ground-based spectroscopic data of HD 181231 has led to the determination of the fundamental and pulsational parameters of the star, including beating effects. This will allow a precise seismic modelling of this star. Based on observations obtained with the CoRoT satellite, with FEROS at the 2.2 m télescope of the La Silla Observatory under the ESO Large Programme LP178.D-0361, with Narval at the Télescope Bernard Lyot of the Pic du Midi Observatory, and collected from the BeSS database. Table 5 is only available in

  8. 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.

  9. 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.

  10. Autostereogram resonators

    NASA Astrophysics Data System (ADS)

    Leavey, Sean; Rae, Katherine; Murray, Adam; Courtial, Johannes

    2012-09-01

    Autostereograms, or "Magic Eye" pictures, are repeating patterns designed to give the illusion of depth. Here we discuss optical resonators that create light patterns which, when viewed from a suitable position by a monocular observer, are autostereograms of the three-dimensional shape of one of the mirror surfaces.

  11. Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model

    NASA Astrophysics Data System (ADS)

    Michtchenko, T. A.; Vieira, R. S. S.; Barros, D. A.; Lépine, J. R. D.

    2017-01-01

    Context. Resonances in the stellar orbital motion under perturbations from the spiral arm structure can play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (in the context of nearly circular orbits), but is not suitable in general. Aims: We expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped groove profiles without any restriction on the stellar orbital configurations, and we expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions. Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes of initial conditions are constructed numerically in order to characterize the phase-space structure and identify the precise location of the co-rotation and Lindblad resonances. The study is complemented by the construction of dynamical power spectra, which provide the identification of fundamental oscillatory patterns in the stellar motion. Results: Our approach allows a precise description of the resonance chains in the whole phase space, giving a broader view of the dynamics of the system when compared to the classical epicyclic approach. We generalize the concept of Lindblad resonances and extend it to cases of resonant orbits with large radial excursions, even for objects in retrograde motion. The analysis of the solar neighbourhood shows that, depending on the current azimuthal phase of the Sun with respect to the spiral arms, a star with solar kinematic parameters (SSP) may evolve in dynamically distinct regions, either inside the stable co-rotation resonance or in a chaotic zone. Conclusions: Our approach contributes to quantifying the domains of resonant orbits and the degree of chaos in the whole Galactic phase-space structure. It may serve as a

  12. Gravity and limb-darkening coefficients for the Kepler, CoRoT, Spitzer, uvby, UBVRIJHK, and Sloan photometric systems

    NASA Astrophysics Data System (ADS)

    Claret, A.; Bloemen, S.

    2011-05-01

    Aims: The complex physics of close binary stars is made even more challenging by the proximity effects that affect it. Understanding the influence of these proximity effects is one of the most important tasks in theoretical stellar astrophysics. It is crucial to know how the specific intensity is distributed over the stellar disk for a correct modelling of the light curves of eclipsing binaries and planetary transits. To provide theoretical input for light curve modelling codes, we present new calculations of gravity- and limb-darkening coefficients for a wide range of effective temperatures, gravities, metallicities, and microturbulent velocities. Methods: We computed limb-darkening coefficients for several atmosphere models, which cover the transmission curves of the Kepler, CoRoT, and Spitzer space missions as well as more widely used passbands (Strömgren, Johnson-Cousins, Sloan). In addition to these computations, which were made adopting the least-square method, we also performed calculations for the bi-parametric approximations by adopting the flux conservation method to provide users with an additional tool to estimate the theoretical error bars. To facilitate the modelling of the effects of tidal and rotational distortions, we computed the gravity-darkening coefficients y(λ) using the same models of stellar atmospheres as for the limb-darkening. Compared to previous work, a more general differential equation was used, which now takes into account local gravity variations and the effects of convection. Results: The limb-darkening coefficients were computed with a higher numerical resolution (100 μ points instead of 15 or 17, as is often used in the ATLAS models), and five equations were used to describe the specific intensities (linear, quadratic, root-square, logarithmic, and a 4-coefficient law). Concerning the gravity-darkening coefficients, the influence of the local gravity on y(λ) is shown as well as the effects of convection, which turn out to be

  13. 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.; hide

    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

  14. 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.

  15. Study of Corotating Interaction Regions in the Ascending Phase of the Solar Cycle: Multi-spacecraft Observations

    NASA Astrophysics Data System (ADS)

    Gonzalez-Esparza, J. A.; Romero-Hernandez, E.; Riley, P.

    2013-07-01

    We combined simultaneous solar wind observations from five different spacecraft: Helios 1, Helios 2, IMP-8, Voyager 1 and Voyager 2, from November 1977 to February 1978 (Carrington rotations 1661 - 1664, ascending phase of Solar Cycle 21). The concurrence of the five trajectories makes this interval unique for the purpose of studying solar wind dynamics during this phase of the cycle. We analyzed the observations identifying five corotating interaction regions (CIRs) and produced maps of interplanetary large-scale features, unifying and summarizing the data. The maps show the compressive events and the magnetic sectors associated with the solar wind streams causing the CIRs. We analyzed the relative position of the stream interfaces immersed within the CIRs. About 70 % of the stream interfaces in this study were located closer to the forward edge of the CIR. From the analysis of the geometry of the stream interfaces, we found that all the CIRs presented latitudinal tilts, having their fronts pointing towards the ecliptic plane and their tails northwards or southwards. These results are in agreement with the origin of the fast streams coming from mid-latitude coronal holes and the predominance of forward shocks over reverse shocks bounding the CIRs, which characterize this phase of the cycle. From the analysis of the ratio of dynamic pressures between fast and slow solar wind streams associated with the CIRs, we found that in about 60 % of the cases the fast stream was transferring momentum to the slow one ahead, but in the rest of the cases the momentum was flowing sunward. This result indicates significant inhomogeneities in the solar wind streams during the ascending phase of the cycle that affect the local form and evolution of CIR events. We did a limited comparison between a global magneto-hydrodynamic (MHD) model of SW flows and the orientation of the SI from in-situ observations, we found, in general, a qualitative agreement between the pressure profiles at

  16. Suprathermal helium in corotating interaction regions: combined observations from SOHO/CELIAS/STOF and ACE/SWICS

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    Context. Energetic particle enhancements that are associated with corotating interaction regions (CIRs) are typically believed to arise from the sunward propagation of particles that are accelerated by CIR-driven shocks beyond 1 AU. It is expected that these sunward-travelling particles will lose energy and scatter, resulting in a turnover of the energy spectra below 0.5 MeV/nuc. However, the turnover has not been observed so far, suggesting that the CIR-associated low-energy suprathermal ions are accelerated locally close to the observer. Aims: We investigate the variability of suprathermal particle spectra from CIR to CIR as well as their evolution and variation as the observer moves away from the rear shock or wave. Methods: Helium data in the suprathermal energy range from the Solar and Heliospheric Observatory/Charge, Element, and Isotope Analysis System/Suprathermal Time-of-Flight (SOHO/CELIAS/STOF) were used for the spectral analysis and were combined with data from the Advanced Composition Explorer/ Solar Wind Ion Composition Spectrometer (ACE/SWICS) in the solar wind energies. Results: We investigated sixteen events: nine clean CIR events, three CIR events with possible contamination from upstream ion events or solar energetic particles (SEPs), and four events that occurred during CIR periods that were dominated by SEPs. Six of the nine clean CIR events showed possible signs of a turnover between 10-40 keV/nuc in the fast solar wind that trails the compression regions. Three of them even showed this behaviour inside the compressed fast wind. The turnover part of the spectra became flatter and shifted from lower to higher energies with increasing connection distance to the reverse shock. The remaining three clean events showed continuous power-law spectra in both the compressed fast wind and fast wind regions, that is, the same behaviour as reported from previous observations. The spectra of the seven remaining events are more variable, that is, they show

  17. Investigation of process temperature and screw speed on properties of a pharmaceutical solid dispersion using corotating and counter-rotating twin-screw extruders.

    PubMed

    Keen, Justin M; Martin, Charlie; Machado, Augie; Sandhu, Harpreet; McGinity, James W; DiNunzio, James C

    2014-02-01

    The use of corotating twin screw hot-melt extruders to prepare amorphous drug/polymer systems has become commonplace. As small molecule drug candidates exiting discovery pipelines trend towards higher MW and become more structurally complicated, the acceptable operating space shifts below the drug melting point. The objective of this research is to investigate the extrusion process space, which should be selected to ensure that the drug is solubilized in the polymer with minimal thermal exposure, is critical in ensuring the performance, stability and purity of the solid dispersion. The properties of a model solid dispersion were investigated using both corotating and counter-rotating hot-melt twin-screw extruders operated at various temperatures and screw speeds. The solid state and dissolution performance of the resulting solid dispersions was investigated and evaluated in context of thermodynamic predictions from Flory-Huggins Theory. In addition, the residence time distributions were measured using a tracer, modelled and characterized. The amorphous content in the resulting solid dispersions was dependent on the combination of screw speed, temperature and operating mode. The counter-rotating extruder was observed to form amorphous solid dispersions at a slightly lower temperature and with a narrower residence time distribution, which also exhibited a more desirable shape. © 2013 Royal Pharmaceutical Society.

  18. 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.

  19. 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.

  20. 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.

  1. Abundance analysis of targets for the COROT/MONS asteroseismology missions. I. Semi-automatic abundance analysis of the gamma Dor star HD 49434

    NASA Astrophysics Data System (ADS)

    Bruntt, H.; Catala, C.; Garrido, R.; Rodríguez, E.; Stütz, C.; Knoglinger, P.; Mittermayer, P.; Bouret, J. C.; Hua, T.; Lignières, F.; Charpinet, S.; Van't Veer-Menneret, C.; Ballereau, D.

    2002-07-01

    One of the goals of the ground-based support program for the COROT and MONS/Römer satellite missions is to select and characterise suitable target stars for the part of the missions dedicated to asteroseismology. While the global atmospheric parameters may be determined with good accuracy from the Strömgren indices, careful abundance analysis must be made for the proposed main targets. This is a time consuming process considering the long list of primary and secondary targets. We have therefore developed new software called VWA for this task. The VWA automatically selects the least blended lines from the atomic line database VALD, and consequently adjusts the abundance in order to find the best match between the calculated and observed spectra. The variability of HD 49434 was discovered as part of COROT ground-based support observations. Here we present a detailed abundance analysis of HD 49434 using VWA. For most elements we find abundances somewhat below the Solar values, in particular we find [Fe/H] = -0.13 +/- 0.14. We also present the results from the study of the variability that is seen in spectroscopic and photometric time series observations. From the characteristics of the variation seen in photometry and in the line profiles we propose that HD 49434 is a variable star of the gamma Doradus type. Based on observations obtained at Observatoire d'Haute Provence, France and at the Observatory of Sierra Nevada, Granada, Spain.

  2. 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

  3. The pulsating nature of large-scale Saharan dust transport as a result of interplays between mid-latitude Rossby waves and the North African Dipole Intensity

    NASA Astrophysics Data System (ADS)

    Cuevas, E.; Gómez-Peláez, A. J.; Rodríguez, S.; Terradellas, E.; Basart, S.; García, R. D.; García, O. E.; Alonso-Pérez, S.

    2017-10-01

    It was previously shown that during August the export of Saharan dust to the Atlantic was strongly affected by the difference of the 700-hPa geopotential height anomaly between the subtropics and the tropics over North Africa, which was termed the North African Dipole Intensity (NAFDI). In this work a more comprehensive analysis of the NAFDI is performed, focusing on the entire summer dust season (June-September), and examining the interactions between the mid-latitude Rossby waves (MLRWs) and NAFDI. Widespread and notable aerosol optical depth (AOD) monthly anomalies are found for each NAFDI-phase over the dust corridors off the Sahara, indicating that NAFDI presents intra-seasonal variability and drives dust transport over both the Mediterranean basin and the North Atlantic. Those summer months with the same NAFDI-phase show similar AOD-anomaly patterns. Variations in NAFDI-phase also control the displacement of the Saharan Heat Low (SHL) westwards or eastwards through horizontal advection of temperature over Morocco-Western Sahara or eastern Algeria-Western Libya, respectively. The connection between the SHL and the NAFDI is quantified statistically by introducing two new daily indexes that account for their respective phases (NAFDI daily index -NAFDIDI-, and SHL longitudinal shift index -SHLLSI-) and explained physically using the energy equation of the atmospheric dynamics. The Pearson's correlation coefficient between the one-day-lag SHLLSI and the NAFDIDI for an extended summer season (1980-2013) is 0.78. A positive NAFDI is associated with the West-phase of the SHL, dust sources intensification on central Algeria, and positive AOD anomalies over this region and the Subtropical North Atlantic. A negative NAFDI is associated with the East-phase of the SHL, and positive AOD anomalies over central-eastern Sahara and the central-western Mediterranean Sea. The results point out that the phase changes of NAFDI at intra-seasonal time scale are conducted by those

  4. Large-Amplitude, Short-Scale Stationary Rossby Waves in the Southern Hemisphere: Observations and Mechanistic Experiments to Determine their Origin.

    NASA Astrophysics Data System (ADS)

    Kalnay, E.; Mo, Kingtse C.; Paegle, J.

    1986-02-01

    Studies by van Loon and Jenne, van Loon et al., Trenberth and others indicate that stationary waves in the Southern Hemisphere are dominated by planetary scales. Kalnay and Halem reported the presence of large amplitude, short-scale stationary waves during the month of January 1979 in the lee of South America and their disappearance in February 1979. In this paper we present further observational evidence of the January waves.We also perform two 15-day forecast experiments with the GLAS Fourth-Order General Circulation Model, and initial conditions corresponding to 5 January and 4 February 1979. These factors reproduce reasonably well the presence of the January waves and their absence in February. Several mechanistic experiments to determine the origin of the waves are then performed.The principal conclusions area) Large amplitude stationary Rossby waves with zonal wavenumber 7 were present between 20° and 40°S both in the South Pacific and east of South America during January 1979. They appear in satellite observations as enhanced bands of high clouds associated with the South Pacific Convergence Zone (SPCZ) and the Amazon. Examination of satellite observations during 1974-79 indicates a correlation between the intensity of stationary cloud bands in the two regions.b) The stationary waves in the lee of South America are not of orographic origin since they are associated with a ridge rather than a trough east of the Andes. A `no Andes' forecast experiment confirms this argument.c) The waves could not be produced by a CISK mechanism suggested by Kalnay and Halem, because of their rather barotropic vertical structure. Sea surface temperature (SST) anomalies in the South Atlantic were of the same scale as the waves, but stronger at the end of January. This, and strong correlation between low level atmospheric cyclonic vorticity and cold SST anomalies indicate that the atmospheric stationary waves were the cause of the ocean temperature anomalies, which in turn

  5. Fluctuations, response, and resonances in a simple atmospheric model

    NASA Astrophysics Data System (ADS)

    Gritsun, Andrey; Lucarini, Valerio

    2017-06-01

    We study the response of a simple quasi-geostrophic barotropic model of the atmosphere to various classes of perturbations affecting its forcing and its dissipation using the formalism of the Ruelle response theory. We investigate the geometry of such perturbations by constructing the covariant Lyapunov vectors of the unperturbed system and discover in one specific case-orographic forcing-a substantial projection of the forcing onto the stable directions of the flow. This results into a resonant response shaped as a Rossby-like wave that has no resemblance to the unforced variability in the same range of spatial and temporal scales. Such a climatic surprise corresponds to a violation of the fluctuation-dissipation theorem, in agreement with the basic tenets of nonequilibrium statistical mechanics. The resonance can be attributed to a specific group of rarely visited unstable periodic orbits of the unperturbed system. Our results reinforce the idea of using basic methods of nonequilibrium statistical mechanics and high-dimensional chaotic dynamical systems to approach the problem of understanding climate dynamics.

  6. 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.

  7. 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.

  8. Galactic rings revisited. II. Dark gaps and the locations of resonances in early-to-intermediate-type disc galaxies

    NASA Astrophysics Data System (ADS)

    Buta, Ronald J.

    2017-10-01

    Dark gaps are commonly seen in early-to-intermediate-type barred galaxies having inner and outer rings or related features. In this paper, the morphologies of 54 barred and oval ringed galaxies have been examined with the goal of determining what the dark gaps are telling us about the structure and evolution of barred galaxies. The analysis is based mainly on galaxies selected from the Galaxy Zoo 2 data base and the Catalogue of Southern Ringed Galaxies. The dark gaps between inner and outer rings are of interest because of their likely association with the L4 and L5 Lagrangian points that would be present in the gravitational potential of a bar or oval. Since the points are theoretically expected to lie very close to the corotation resonance (CR) of the bar pattern, the gaps provide the possibility of locating corotation in some galaxies simply by measuring the radius rgp of the gap region and setting rCR=rgp. With the additional assumption of generally flat rotation curves, the locations of other resonances can be predicted and compared with observed morphological features. It is shown that this `gap method' provides remarkably consistent interpretations of the morphology of early-to-intermediate-type barred galaxies. The paper also brings attention to cases where the dark gaps lie inside an inner ring, rather than between inner and outer rings. These may have a different origin compared to the inner/outer ring gaps.

  9. 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…

  10. A search for pulsations in the HgMn star HD 45975 with CoRoT photometry and ground-based spectroscopy

    NASA Astrophysics Data System (ADS)

    Morel, T.; Briquet, M.; Auvergne, M.; Alecian, G.; Ghazaryan, S.; Niemczura, E.; Fossati, L.; Lehmann, H.; Hubrig, S.; Ulusoy, C.; Damerdji, Y.; Rainer, M.; Poretti, E.; Borsa, F.; Scardia, M.; Schmid, V. S.; Van Winckel, H.; De Smedt, K.; Pápics, P. I.; Gameiro, J. F.; Waelkens, C.; Fagas, M.; Kamiński, K.; Dimitrov, W.; Baglin, A.; Michel, E.; Dumortier, L.; Frémat, Y.; Hensberge, H.; Jorissen, A.; Van Eck, S.

    2014-01-01

    The existence of pulsations in HgMn stars is still being debated. To provide the first unambiguous observational detection of pulsations in this class of chemically peculiar objects, the bright star HD 45975 was monitored for nearly two months by the CoRoT satellite. Independent analyses of the light curve provide evidence of monoperiodic variations with a frequency of 0.7572 d-1 and a peak-to-peak amplitude of ~2800 ppm. Multisite, ground-based spectroscopic observations overlapping the CoRoT observations show the star to be a long-period, single-lined binary. Furthermore, with the notable exception of mercury, they reveal the same periodicity as in photometry in the line moments of chemical species exhibiting strong overabundances (e.g., Mn and Y). In contrast, lines of other elements do not show significant variations. As found in otherHgMn stars, the pattern of variability consists in an absorption bump moving redwards across the line profiles. We argue that the photometric and spectroscopic changes are more consistent with an interpretation in terms of rotational modulation of spots at the stellar surface. In this framework, the existence of pulsations producing photometric variations above the ~50 ppm level is unlikely in HD 45975. This provides strong constraints on the excitation/damping of pulsation modes in this HgMn star. 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. This work is based on observations collected at La Silla and Paranal Observatories, ESO (Chile), with the HARPS and UVES spectrographs at the 3.6-m and very large telescopes, under programmes LP185.D-0056 and 287.D-5066. It is also based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias

  11. 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

  12. Transiting exoplanets from the CoRoT space mission. II. CoRoT-Exo-2b: a transiting planet around an active G star

    NASA Astrophysics Data System (ADS)

    Alonso, R.; Auvergne, M.; Baglin, A.; Ollivier, M.; Moutou, C.; Rouan, D.; Deeg, H. J.; Aigrain, S.; Almenara, J. M.; Barbieri, M.; Barge, P.; Benz, W.; Bordé, P.; Bouchy, F.; de La Reza, R.; Deleuil, M.; Dvorak, R.; Erikson, A.; Fridlund, M.; Gillon, M.; Gondoin, P.; Guillot, T.; Hatzes, A.; Hébrard, G.; Kabath, P.; Jorda, L.; Lammer, H.; Léger, A.; Llebaria, A.; Loeillet, B.; Magain, P.; Mayor, M.; Mazeh, T.; Pätzold, M.; Pepe, F.; Pont, F.; Queloz, D.; Rauer, H.; Shporer, A.; Schneider, J.; Stecklum, B.; Udry, S.; Wuchterl, G.

    2008-05-01

    Context: The CoRoT mission, a pioneer in exoplanet searches from space, has completed its first 150 days of continuous observations of ~12 000 stars in the galactic plane. An analysis of the raw data identifies the most promising candidates and triggers the ground-based follow-up. Aims: We report on the discovery of the transiting planet CoRoT-Exo-2b, with a period of 1.743 days, and characterize its main parameters. Methods: We filter the CoRoT raw light curve of cosmic impacts, orbital residuals, and low frequency signals from the star. The folded light curve of 78 transits is fitted to a model to obtain the main parameters. Radial velocity data obtained with the SOPHIE, CORALIE and HARPS spectrographs are combined to characterize the system. The 2.5 min binned phase-folded light curve is affected by the effect of sucessive occultations of stellar active regions by the planet, and the dispersion in the out of transit part reaches a level of 1.09×10-4 in flux units. Results: We derive a radius for the planet of 1.465 ± 0.029 R_Jup and a mass of 3.31 ± 0.16 M_Jup, corresponding to a density of 1.31 ± 0.04 g/cm^3. The large radius of CoRoT-Exo-2b cannot be explained by current models of evolution of irradiated planets. Based on observations obtained with CoRoT, a space project operated by the French Space Agency, CNES, with participation of the Science Programme of ESA, ESTEC/RSSD, Austria, Belgium, Brazil, Germany and Spain; and on observations made with SOPHIE spectrograph at Observatoire de Haute Provence, France (PNP.07 A.MOUT), CORALIE, and HARPS spectrograph at ESO La Silla Observatroy (079.C-0127/F)). Table 2 is only available in electronic form at http://www.aanda.org

  13. The CoRoT B-type binary HD 50230: a prototypical hybrid pulsator with g-mode period and p-mode frequency spacings⋆

    NASA Astrophysics Data System (ADS)

    Degroote, P.; Aerts, C.; Michel, E.; Briquet, M.; Pápics, P. I.; Amado, P.; Mathias, P.; Poretti, E.; Rainer, M.; Lombaert, R.; Hillen, M.; Morel, T.; Auvergne, M.; Baglin, A.; Baudin, F.; Catala, C.; Samadi, R.

    2012-06-01

    Context. B-type stars are promising targets for asteroseismic modelling, since their frequency spectrum is relatively simple. Aims: We deduce and summarise observational constraints for the hybrid pulsator, HD 50230, earlier reported to have deviations from a uniform period spacing of its gravity modes. The combination of spectra and a high-quality light curve measured by the CoRoT satellite allow a combined approach to fix the position of HD 50230 in the HR diagram. Methods: To describe the observed pulsations, classical Fourier analysis was combined with short-time Fourier transformations and frequency spacing analysis techniques. Visual spectra were used to constrain the projected rotation rate of the star and the fundamental parameters of the target. In a first approximation, the combined information was used to interpret multiplets and spacings to infer the true surface rotation rate and a rough estimate of the inclination angle. Results: We identify HD 50230 as a spectroscopic binary and characterise the two components. We detect the simultaneous presence of high-order g modes and low-order p and g-modes in the CoRoT light curve, but were unable to link them to line profile variations in the spectroscopic time series. We extract the relevant information from the frequency spectrum, which can be used for seismic modelling, and explore possible interpretations of the pressure mode spectrum. 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. Based on observations made with the ESO telescopes at La Silla Observatory under the ESO Large Programme LP182.D-0356, and on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and on observations obtained with the HERMES

  14. 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.

  15. 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.

  16. 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.

  17. Structural and core parameters of the hot B subdwarf KPD 0629-0016 from CoRoT g-mode asteroseismology

    NASA Astrophysics Data System (ADS)

    Van Grootel, V.; Charpinet, S.; Fontaine, G.; Green, E. M.; Brassard, P.

    2010-12-01

    Context. The asteroseismic exploitation of long period, g-mode hot B subdwarf pulsators (sdBVs), undermined so far by limitations associated with ground-based observations, has now become possible, thanks to high quality data obtained from space such as those recently gathered with the CoRoT (COnvection, ROtation, and planetary Transits) satellite. Aims: We propose a detailed seismic analysis of the sdBVs star KPD 0629-0016, the first compact pulsator monitored with CoRoT, using the g-mode pulsations recently uncovered by that space-borne observatory during short run SRa03. Methods: We use a forward modeling approach on the basis of our latest sdB models, which are now suitable for the accurate computation of the g-mode pulsation properties. The simultaneous match of the independent periods observed in KPD 0629-0016 with those of the models leads objectively to the identification of the pulsation modes and, more importantly, to the determination of the structural and core parameters of the star. Results: The optimal model we found closely reproduces the 18 observed periods retained in our analysis at a 0.23% level on average. These are identified as low-degree (ℓ = 1 and 2), intermediate-order (k = -9 through -74) g-modes. The structural and core parameters for KPD 0629-0016 are the following (formal fitting errors only): Teff = 26 290 ± 530 K, log g = 5.450 ± 0.034, M_* = 0.471 ± 0.002 M⊙, log (Menv/M_*) = -2.42 ± 0.07, log (1-Mcore/M_*) = -0.27 ± 0.01, and Xcore(C+O) = 0.41 ± 0.01. We additionally derive an age of 42.6 ± 1.0 Myr after the zero-age extreme horizontal branch, the radius R = 0.214 ± 0.009 R⊙, the luminosity L = 19.7 ± 3.2 L⊙, the absolute magnitude MV = 4.23 ± 0.13, the reddening index E(B-V) = 0.128 ± 0.023, and the distance d = 1190 ± 115 pc. Conclusions: The advent of high-precision time-series photometry from space with instruments like CoRoT now allows as demonstrated with KPD 0629-0016 the full exploitation of g-modes as

  18. An asteroseismic study of the β Cephei CoRoT main target HD 180642: results from the ground-based campaign

    NASA Astrophysics Data System (ADS)

    Briquet, M.; Uytterhoeven, K.; Morel, T.; Aerts, C.; De Cat, P.; Mathias, P.; Lefever, K.; Miglio, A.; Poretti, E.; Martín-Ruiz, S.; Paparó, M.; Rainer, M.; Carrier, F.; Gutiérrez-Soto, J.; Valtier, J. C.; Benkő, J. M.; Bognár, Zs.; Niemczura, E.; Amado, P. J.; Suárez, J. C.; Moya, A.; Rodríguez-López, C.; Garrido, R.

    2009-09-01

    The β Cephei star HD 180642 was observed by the CoRoT satellite during a run of 156 days in 2007. The space white light photometry revealed the rich frequency spectrum of the star (Degroote et al. 2009). In the present study, we provide additional information on the target, based on both ground-based multi-colour photometry and high-resolution spectroscopy. We place our object in the (Teff, log g) diagram. In addition, we derive the chemical abundances of several elements as well as the metallicity of HD 180642. Finally, we put constraints on the identification of some modes. All these observational constraints will be used to compute stellar models of the target.

  19. 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.

  20. Transiting exoplanets from the CoRoT space mission. V. CoRoT-Exo-4b: stellar and planetary parameters

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

    Aims: The CoRoT satellite has announced its fourth transiting planet (Aigrain et al. 2008, A&A, 488, L43) with space photometry. We describe and analyse complementary observations of this system performed to establish the planetary nature of the transiting body and to estimate the fundamental parameters of the planet and its parent star. Methods: We have analysed high precision radial-velocity data, ground-based photometry, and high signal-to-noise ratio spectroscopy. Results: The parent star CoRoT-Exo-4 (2MASS 06484671-0040219) is a late F-type star of mass of 1.16 M⊙ and radius of 1.17 R⊙. The planet has a circular orbit with a period of 9.20205 d. The planet radius is 1.19 R_Jup and the mass is 0.72 M_Jup. It is a gas-giant planet with a “normal” internal structure of mainly H and He. CoRoT-Exo-4b has the second longest period of the known transiting planets. It is an important discovery since it occupies an empty area in the mass-period diagram of transiting exoplanets. Based on observations obtained with CoRoT, a space project operated by the French Space Agency, CNES, with participation of the Science Programme of ESA, ESTEC/RSSD, Austria, Belgium, Brazil, Germany and Spain; and on observations made with the SOPHIE spectrograph at Observatoire de Haute Provence, France (PNP.07B.MOUT), and the HARPS spectrograph at ESO La Silla Observatory (079.C-0127/F). Table 2