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An overview is presented of several diverse branches of work in the area of effectively 2D fluid equilibria which have in common that they are constrained by an infinite number of conservation laws. Broad concepts, and the enormous variety of physical phenomena that can be explored, are highlighted. These span, roughly in order of increasing complexity, Euler flow, nonlinear Rossby waves, 3D axisymmetric flow, shallow water dynamics, and 2D magnetohydrodynamics. The classical field theories describing these systems bear some resemblance to perhaps more familiar fluctuating membrane and continuous spin models, but the fluid physics drives these models into unconventional regimes exhibiting large scale jet and eddy structures. From a dynamical point of view these structures are the end result of various conserved variable forward and inverse cascades. The resulting balance between large scale structure and small scale fluctuations is controlled by the competition between energy and entropy in the system free energy, in turn highly tunable through setting the values of the conserved integrals. Although the statistical mechanical description of such systems is fully self-consistent, with remarkable mathematical structure and diversity of solutions, great care must be taken because the underlying assumptions, especially ergodicity, can be violated or at minimum lead to exceedingly long equilibration times. Generalization of the theory to include weak driving and dissipation (e.g., non-equilibrium statistical mechanics and associated linear response formalism) could provide additional insights, but has yet to be properly explored. [ABSTRACT FROM AUTHOR]

This study identifies general characteristics of methods to estimate the absolute range between an acoustic transmitter and a receiver in the deep ocean. The data are from three days of the PhilSea10 experiment with a single fixed transmitter depth (∼998 m) and 150 receiver depths (∼210–5388 m) of known location, and a great-circle transmitter-receiver distance of ∼510 km. The proposed ranging methods compare observed acoustic records with synthetic records computed through the HYCOM (hybrid coordinate ocean model) model. More than 8900 transmissions over 3 days characterize the statistical variation of range errors. Reliable ranging methods de-emphasize the parts of the data records least likely to be reproduced by the synthetics, which include arrival amplitudes, the later parts of the acoustic records composed of nearly horizontally launched rays (i.e., the finale), and waves that sample a narrow span of ocean depths. The ranging methods proposed normalize amplitudes, measure travel times, or reject parts of the waveforms beyond a critical time. All deliver reliable range estimates based on the time and path-averaged HYCOM model, although the final method performs best. The principles behind these methods are transportable and expected to provide reliable range estimates in different deep water settings. [ABSTRACT FROM AUTHOR]

The work reported here details basic validation of our advanced physics-based electromagnetic induction forward and inverse models against data collected by the Naval Research Laboratory Time-Domain Electromagnetic Multisensor Towed Array Detection System platform. The data were collected under laboratory-type conditions using both artificial spheroidal targets and real unexploded ordnance (UXO). The artificial target models are essentially exact and enable detailed comparison of theory and data in support of measurement platform characterization and target identification. Real UXO targets cannot be treated exactly, but it is demonstrated that quantitative comparisons of the data with the spheroid models nevertheless aid in extracting key target discrimination information, such as target geometry and hollow target shell thickness. [ABSTRACT FROM AUTHOR]

The equilibrium theory of the 2D magnetohydrodynamic equations is derived, accounting for the full infinite hierarchies of conserved integrals. An exact description in terms of two coupled elastic membranes emerges, producing long-ranged correlations between the magnetic and velocity fields. This is quite different from the results of previous variational treatments, which relied on a local product ansatz for the thermodynamic Gibbs distribution. The equilibria display the same type of coherent structures, such as compact eddies and zonal jets, previously found in pure fluid equilibria. Possible consequences of this for recent simulations of the solar tachocline are discussed. [ABSTRACT FROM AUTHOR]

A concise and somewhat personal review of the problem of superfluidity and quantum criticality in regular and disordered interacting Bose systems is given, concentrating on general features and important symmetries that are exhibited in different parts of the phase diagram, and that govern the different possible types of critical behavior. A number of exact results for various insulating phase boundaries, which may be used to constrain the results of numerical simulations, can be derived using large rare region type arguments. The nature of the insulator-superfluid transition is explored through general scaling arguments, exact model calculations in one dimension, numerical results in two dimensions, and approximate renormalization group results in higher dimensions. Experiments on 4He adsorbed in porous Vycor glass, on thin film superconductors, and magnetically trapped atomic vapors in a periodic optical potential are used to illustrate many of the concepts. [ABSTRACT FROM AUTHOR]

Abstract: A three-dimensional spectral analysis of Topex altimeter data reveals a large meridional component k y of the wavevector k for baroclinic Rossby waves of all timescales. Its existence necessitates some refinements in our estimates of certain basic properties of the Rossby wave field. In particular, by taking into account an actual off-zonal direction of k (often exceeding 70°), one finds that the wavelength, phase speed, and group velocity of mid-latitude Rossby waves (with periods less than 2 years) are much smaller than they appear to be on the assumption of a purely zonal wavenumber vector. Because of a shorter wavelength (yielding kL as high as 0.6, where L is the Rossby radius of deformation), these waves are essentially dispersive. Their group velocity vector may depart from zonal by more than 30°. An important intrinsic feature of the wave spectrum confirmed by our analysis is a broad-band distribution with respect to k y . Some of the dynamical implications of the large k y /k x ratio are discussed. [Copyright &y& Elsevier]

We show that rotating shallow water dynamics possesses an approximate (adiabatic-type) positive quadratic invariant, which exists not only at midlatitudes (where its analog in the quasigeostrophic equation has been previously investigated), but near the equator as well (where the quasigeostrophic equation is inapplicable). When deriving the extra invariant we find two kinds of small denominators: (i) those due to the triad resonances (as in the case of the quasigeostrophic equation) and (ii) those due to the equatorial limit, when the Rossby radius of deformation becomes infinite. We show that both kinds of small denominators can be canceled. The presence of the extra invariant can lead to the generation of zonal jets. We find that this tendency should be especially pronounced near the equator. A similar invariant occurs in magnetically confined fusion plasmas and can lead to the emergence of zonal flows. [ABSTRACT FROM AUTHOR]

Abstract: A new statistical approach to analyzing large-scale oceanic motions characterized by strong statistical inhomogeneity in the meridional direction is developed and applied to a 9-year series of satellite altimeter observations in the Tropical Pacific between 20 S and 20N. A special treatment of meridional variations permits quantitative characterization of latitudinally alternating, zonally elongated features of the sea surface height field. Their frequency and length scales demonstrate that these features pertain to baroclinic large-scale wave motions, such as highly irregular Rossby waves. Since the sea surface height field at each latitude is generally found to be dominated by a few strong spectral peaks (semi-annual, annual, near-tetra-annual) for both westward and eastward propagating motions, a dominant wavevector may be associated with each such selected range of temporal and zonal scales. The meridional component of the wavevector is derived from the phase shift of the cross-spectrum between two neighboring latitudes apart. The latitude dependence of these wavevectors may be instructively represented as a set of wavefronts that provide a global picture of the dominant flows. [Copyright &y& Elsevier]