scholarly journals Wave propagation in semiconvective regions of giant planets

2020 ◽  
Vol 493 (4) ◽  
pp. 5788-5806
Author(s):  
C M Pontin ◽  
A J Barker ◽  
R Hollerbach ◽  
Q André ◽  
S Mathis
Keyword(s):  
Wave Propagation ◽  
Internal Waves ◽  
Spherical Body ◽  
Giant Planets ◽  
Small Scale ◽  
Compositional Gradient ◽  
Tidal Dissipation ◽  
The Core ◽  
Resonant Modes ◽  
Diffusive Convection

ABSTRACT Recent observations of Jupiter and Saturn suggest that heavy elements may be diluted in the gaseous envelope, providing a compositional gradient that could stabilize ordinary convection and produce a stably stratified layer near the core of these planets. This region could consist of semiconvective layers with a staircase-like density profile, which have multiple convective zones separated by thin stably stratified interfaces, as a result of double-diffusive convection. These layers could have important effects on wave propagation and tidal dissipation that have not been fully explored. We analyse the effects of these layers on the propagation and transmission of internal waves within giant planets, extending prior work in a local Cartesian model. We adopt a simplified global Boussinesq planetary model in which we explore the internal waves in a non-rotating spherical body. We begin by studying the free modes of a region containing semiconvective layers. We then analyse the transmission of internal waves through such a region. The free modes depend strongly on the staircase properties, and consist of modes with both internal and interfacial gravity wave-like behaviour. We determine the frequency shifts of these waves as a function of the number of steps to explore their potential to probe planetary internal structures. We also find that wave transmission is strongly affected by the presence of a staircase. Very large wavelength waves are transmitted efficiently, but small-scale waves are only transmitted if they are resonant with one of the free modes. The effective size of the core is therefore larger for non-resonant modes.

scholarly journals On a new formulation for energy transfer between convection and fast tides with application to giant planets and solar type stars

2021 ◽  
Author(s):  
Caroline Terquem
Keyword(s):  
Shear Flow ◽  
Convective Flow ◽  
Large Scale ◽  
Dissipation Factor ◽  
Giant Planets ◽  
Small Scale ◽  
Late Type ◽  
Mean Flow ◽  
Tidal Dissipation ◽  
Tidal Period

Abstract All the studies of the interaction between tides and a convective flow assume that the large scale tides can be described as a mean shear flow which is damped by small scale fluctuating convective eddies. The convective Reynolds stress is calculated using mixing length theory, accounting for a sharp suppression of dissipation when the turnover timescale is larger than the tidal period. This yields tidal dissipation rates several orders of magnitude too small to account for the circularization periods of late–type binaries or the tidal dissipation factor of giant planets. Here, we argue that the above description is inconsistent, because fluctuations and mean flow should be identified based on the timescale, not on the spatial scale, on which they vary. Therefore, the standard picture should be reversed, with the fluctuations being the tidal oscillations and the mean shear flow provided by the largest convective eddies. We assume that energy is locally transferred from the tides to the convective flow. Using this assumption, we obtain values for the tidal Q factor of Jupiter and Saturn and for the circularization periods of PMS binaries in good agreement with observations. The timescales obtained with the equilibrium tide approximation are however still 40 times too large to account for the circularization periods of late–type binaries. For these systems, shear in the tachocline or at the base of the convective zone may be the main cause of tidal dissipation.

scholarly journals Strong Modulation of Short Wind Waves and Ka-Band Radar Return Due to Internal Waves in the Presence of Surface Films. Theory and Experiment

2021 ◽  
Vol 13 (13) ◽  
pp. 2462
Author(s):  
Stanislav A. Ermakov ◽  
Irina A. Sergievskaya ◽  
Ivan A. Kapustin
Keyword(s):  
Phase Velocity ◽  
Internal Waves ◽  
Wind Waves ◽  
Strong Increase ◽  
Small Scale ◽  
Surface Films ◽  
Ka Band ◽  
Steady Current ◽  
Backscatter Modulation ◽  
Resonance Surface

Strong variability of Ka-band radar backscattering from short wind waves on the surface of water covered with surfactant films in the presence of internal waves (IW) was studied in wave tank experiments. It has been demonstrated that modulation of Ka-band radar return due to IW strongly depends on the relationship between the phase velocity of IW and the velocity of drifting surfactant films. An effect of the strong increase in surfactant concentration was revealed in convergent zones, associated with IW orbital velocities in the presence of a “resonance” surface steady current, the velocity of which was close to the IW phase velocity. A phenomenological model of suppression and modulations in the spectrum of small-scale wind waves due to films and IW was elaborated. It has been shown that backscatter modulation could not be explained by the modulation of free (linear) millimeter-scale Bragg waves, but was associated with the modulation of bound (parasitic) capillary ripples generated by longer, cm–dm-scale waves—a “cascade” modulation mechanism. Theoretical analysis based on the developed model was found to be consistent with experiments. Field observations which qualitatively illustrated the effect of strong modulation of Ka-band radar backscatter due to IW in the presence of resonance drift of surfactant films are presented.

A multi-layer model for nonlinear internal wave propagation in shallow water

2012 ◽  
Vol 695 ◽  
pp. 341-365 ◽  
Author(s):  
Philip L.-F. Liu ◽  
Xiaoming Wang
Keyword(s):  
Wave Propagation ◽  
Internal Wave ◽  
Shallow Water ◽  
Internal Waves ◽  
Bottom Topography ◽  
Laboratory Data ◽  
Constant Density ◽  
Layer Model ◽  
Fluid System ◽  
Nonlinear Internal Wave

AbstractIn this paper, a multi-layer model is developed for the purpose of studying nonlinear internal wave propagation in shallow water. The methodology employed in constructing the multi-layer model is similar to that used in deriving Boussinesq-type equations for surface gravity waves. It can also be viewed as an extension of the two-layer model developed by Choi & Camassa. The multi-layer model approximates the continuous density stratification by an $N$-layer fluid system in which a constant density is assumed in each layer. This allows the model to investigate higher-mode internal waves. Furthermore, the model is capable of simulating large-amplitude internal waves up to the breaking point. However, the model is limited by the assumption that the total water depth is shallow in comparison with the wavelength of interest. Furthermore, the vertical vorticity must vanish, while the horizontal vorticity components are weak. Numerical examples for strongly nonlinear waves are compared with laboratory data and other numerical studies in a two-layer fluid system. Good agreement is observed. The generation and propagation of mode-1 and mode-2 internal waves and their interactions with bottom topography are also investigated.

Kalmag: a high spatio temporal model of the Geomagnetic field

2021 ◽  
Author(s):  
Julien Baerenzung ◽  
Matthias Holschneider
Keyword(s):  
Geomagnetic Field ◽  
Learning Algorithm ◽  
Dynamical Evolution ◽  
Small Scale ◽  
Large Set ◽  
The Core ◽  
Resolution Model ◽  
Auto Regressive ◽  
Spatio Temporal ◽  
Marine Vessels

<p>We present a new high resolution model of the Geomagnetic field spanning the last 121 years. The model derives from a large set of data taken by low orbiting satellites, ground based observatories, marine vessels, airplane and during land surveys. It is obtained by combining a Kalman filter to a smoothing algorithm. Seven different magnetic sources are taken into account. Three of them are of internal origin. These are the core, the lithospheric  and the induced / residual ionospheric fields. The other four sources are of external origin. They are composed by a close, a remote and a fluctuating magnetospheric fields as well as a source associated with field aligned currents. The dynamical evolution of each source is prescribed by an auto regressive process of either first or second order, except for the lithospheric field which is assumed to be static. The parameters of the processes were estimated through a machine learning algorithm with a sample of data taken by the low orbiting satellites of the CHAMP and Swarm missions. In this presentation we will mostly focus on the rapid variations of the core field, and the small scale lithospheric field.  We will also discuss the nature of model uncertainties and the limitiations they imply.</p>

Plasma Resource Recovery Technology: Converting Waste to Energy and Valuable Products

2005 ◽  
Author(s):  
Pierre Carabin ◽  
Gillian Holcroft
Keyword(s):  
Carbon Monoxide ◽  
Construction Material ◽  
Resource Recovery ◽  
Waste To Energy ◽  
Small Scale ◽  
Cruise Ship ◽  
Plasma Flame ◽  
Fuel Gas ◽  
The Core ◽  
Core Technology

Plasma Resource Recovery (PRR) is a revolutionary technology that can treat virtually any type of waste by combining gasification with vitrification. Vitrification produces inert slag that can be used as a construction material. Gasification produces a fuel gas containing carbon monoxide (CO) and hydrogen (H2), used for cogeneration of electricity and steam. The plasma fired eductor which is the core technology of the PRR system is presently being used commercially on a cruise ship at a scale of 5 TPD. The capabilities of the PRR technology have been demonstrated in a pilot plant, at a rate of up to 2 TPD of various types of waste. Because of the high intensity of the plasma flame and the reduced amounts of gases produced in a gasification system, compared to traditional combustion systems, the PRR system is typically very compact. As such, the PRR technology opens the door for a decentralized, small scale approach to waste management.

Ocean Internal Waves as Sources of Small-Scale Patchiness in Seabird Distribution on the Blake Plateau

The Auk ◽  
1987 ◽  
Vol 104 (1) ◽  
pp. 129-133 ◽  
Author(s):  
J. Christopher Haney
Keyword(s):  
Internal Waves ◽  
Small Scale

Carissimi's Tonal System and the Function of Transposition in the Expansion of Tonality

2002 ◽  
Vol 19 (2) ◽  
pp. 264-305
Author(s):  
Beverly Stein
Keyword(s):  
Final Section ◽  
17Th Century ◽  
Small Scale ◽  
The Core ◽  
The One ◽  
Relationship Of ◽  
Organizing Principles ◽  
Tonal System

The question of 17th-century tonality has intrigued scholars for years: how to make sense of a repertoire in which modal concepts appear to coexist with elements of common-practice tonality. Although the system of modes and that of modern tonality are different constructions, the aspect of functional tonality that allows for the presence of major and minor keys at all 12 levels of transposition developed in part from an extension of a technique carried over from modal practice, that of transposition of mode. Nowhere is this process of tonal expansion based on the concept of transposition of mode as clear or as well structured as in the music of Giacomo Carissimi (1605-1674), the Roman composer of oratorios, cantatas, and motets whose output spans the central 40 years of the 17th century. A close examination of Carissimi's music provides us with a snapshot of the expansion of tonality via transposition and, in addition, offers important suggestions for understanding the tonal practices of contemporaries such as Monteverdi and Cavalli. In Carissimi's music, four basic tonalities are still clearly distinguishable, recognizable through unique and predictable cadence patterns. They appear at transposition levels ranging from the three-flat to the three-sharp systems, with the one-flat system conspicuous in its absence. As shown, the core of eight central keys demonstrates key pairing in a way that models the traditional authentic-plagal relationship of modes. An overview of Carissimi's tonal system demonstrates how the ap- parent coexistence of functional tonality and much older concepts of mode and hexachord can be understood to be part of a rational and organized system. This study explores Carissimi's tonal scheme through an examination of his cantatas, the repertoire displaying the widest tonal range. Based on characteristic cadence frequencies, opening transpositions, and previously unrecognized standard cadence patterns, it is possible to determine the nature of the four primary tonalities and their relationships to one another. These cadence patterns also appear as organizing principles in works of several other 17th-century composers and suggest future avenues of research. The final section summarizes the conservative and progressive features of Carissimi's tonal system, relates his practice to discussion of transposition in two popular treatises of the time, Giovanni Maria Bononcini's Musica prattico and Lorenzo Penna's Li primi albori musicali, and compares Carissimi's practice to the system of church keys (based on common transpositions of the psalm tones) prevalent in the 17th century. A study of Carissimi's cantatas thus reveals the existence of a truly distinct 17th-century tonal practice which functions on its own terms at the same time as it exhibits concepts derived from traditional modal and hexachordal theory, as well as contemporary practices of psalmody and small-scale functional tonality.

scholarly journals Education for Sustainability: Developing Ecocritical Literature Circles in the Student Teacher Classroom

2019 ◽  
Vol 10 (1) ◽  
pp. 5-19
Author(s):  
Lykke Guanio-Uluru
Keyword(s):  
Science Fiction ◽  
Student Teachers ◽  
Young Adult Literature ◽  
Literature Circles ◽  
Student Feedback ◽  
Education For Sustainability ◽  
Literary Texts ◽  
Small Scale ◽  
The Core ◽  
Literature Circle

Abstract How can student-teachers learn efficient ways to encourage sustainability thinking in their pupils and fulfil the competence aims on sustainability outlined in national subject curriculums as a response to UNESCO’s programme on Education for Sustainable Development, ESD? The core hypothesis of this project was that tailored literature circles, focused on the ecocritical aspects of literary texts, would make student-teachers aware of how they can use literature as a process to reflect on sustainability. This would enable them to incorporate sustainability thinking into their own teaching practices. The project’s tailoring of the standard literature circle roles (Daniels 1994, 2002, 2006) involved the design of reading roles that highlighted ecocritical and generic aspects of the studied texts and the application of an analytical matrix developed by literary scholars researching the representation of nature in children’s and young adult literature. This article presents the results of a small-scale study testing the ecocritical literature circles approach and its impact on student-teachers’ conception of their own ability to meet the competence aims on sustainability in their teaching. The intervention included lectures on ecocriticism and on the posthuman debate prior to the literature circles and student feedback through pre- and post-circle questionnaires. It was implemented in the teacher-training classroom, working with dystopian science fiction texts for young adults. These texts present the reader with visions of the future. The study showed that the ecocritical literature circles, and in particular the ecocritical reading roles, were considered useful by the participating student-teachers. The participants also reported a significant increase in confidence relative to their own ability to discuss sustainability issues with their pupils.

Wave Propagation and Power Flow Analysis of Sandwich Structures With Internal Absorbers

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
J. S. Chen ◽  
R. T. Wang
Keyword(s):  
Wave Propagation ◽  
Power Flow ◽  
Wave Attenuation ◽  
Sandwich Structures ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Continuum Models ◽  
Sandwich Beams ◽  
The Core ◽  
In Series

This study examines wave attenuation and power flow characteristics of sandwich beams with internal absorbers. Two types of absorbing systems embedded in the core are considered, namely, a conventional spring-mass-dashpot system having a mass with a spring and a dashpot in parallel, and a relaxation system containing an additional relaxation spring added in series with the dashpot. Analytical continuum models used for interpreting the attenuation behavior of sandwich structures are presented. Through the analysis of the power flowing into the structure, the correlation of wave attenuation and energy blockage is revealed. The reduction in the power flow indicates that some amount of energy produced by the external force can be effectively obstructed by internal absorbers. The effects of parameters on peak attenuation, bandwidth, and power flow are also studied.

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