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At least 1,747 records · Page 97

A scalable wave resource assessment methodology: Application to U.S. waters

Waves deliver large quantities of energy to populated coastlines around the world, and wave energy technology research and development has accelerated over the last two decades. Throughout this time national and regional resource assessments have utilized disparate methodologies, which can cause confusion and skepticism. Here, in this work, we describe a theoretical wave resource assessment methodology that addresses many of the major areas of inconsistency and debate. Applying this revised methodology to U.S. waters, we find the theoretical U.S. wave energy resource to be 3300 TWh/yr, with region totals of 2000 TWh/yr in Alaska, 510 TWh/yr along the U.S. west coast, 380 TWh/yr in Hawaii, 290 TWh/yr along the east coast, 69 TWh/yr in the Gulf of Mexico, and 17 TWh/yr in Puerto Rico and the U.S. Virgin Islands. We also find significant uncertainty in these estimates associated with the underlying model dataset, which emphasizes the importance of thorough model validation and calibration as well as quantifying uncertainty.

16 TIDAL AND WAVE POWER↗

Analysis of Electric and Magnetic Lightning-Generated Wave Amplitudes Measured by the Van Allen Probes

Herein we provide a statistical analysis of both electric and magnetic field wave amplitudes of very low frequency lightning-generated waves (LGWs) based on the equivalent of 11.5 years of observations made by the Van Allen Probes encompassing ~24.6 × 10 6 survey mode measurements. We complement this analysis with data from the ground-based World Wide Lightning Location Network to explore differences between satellite and ground-based measurements. LGW mean amplitudes are found to be low compared with other whistler mode waves (1 ± 1.6 pT and 19 ± 59 μV/m). Extreme events (1/5,000) can reach 100 pT and contributes strongly to the mean power below $L$ = 2. We find excellent correlations between World Wide Lightning Location Network-based power and wave amplitudes in space at various longitudes. We reveal strong dayside ionospheric damping of the LGW electric field. LGW amplitudes drop for $L$ < 2, contrary to the Earth's intense equatorial lightning activity. We conclude that it is difficult for equatorial LGW to propagate and remain at $L$ < 2.

Electric wave power↗

Nonlinear coupling of electromagnetic and electron acoustic waves in multi-species degenerate astrophysical plasma

Nonlinear wave-coupling is studied in a multispecies degenerate astrophysical plasma consisting of two electron species (at different temperatures): a highly degenerate main component plus a smaller classical relativistic flow immersed in a static neutralizing ion background. It is shown that the high frequency electromagnetic waves through their strong nonlinear interactions with the electron-acoustic waves [sustained by a multielectron component (degenerate) plasma surrounding a compact astrophysical object] can scatter to lower frequencies so that the radiation observed faraway will be spectrally shifted downward. It is also shown that, under definite conditions, the electromagnetic waves could settle into stationary solitonic states. It is expected that the effects of such structures may persist as detectable signatures in forms of modulated micropulses in the radiation observed far away from the accreting compact object. Both these effects will advance our abilities to interpret the radiation coming out of the compact objects.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Hall MHD waves: A fundamental departure from their MHD counterparts

It is demonstrated through a succinct derivation as to how the linear waves in Hall magnetohydrodynamics (HMHD) constitute a fundamental departure from the standard MHD waves. Apart from modifying the conventional MHD spectrum, the Hall current induces a distinct and new branch consisting of purely circularly polarized waves that may become the representative shear waves.

Astrophysics↗

On Building Predictive Digital Twin Incorporating Wave Predicting Capabilities: Case Study on UMaine Experimental Campaign - FOCAL

The response of floating wind turbines (FWT) are susceptible to stochastic wave variations. For the optimal operation of FWT, a comprehensive understanding of the phaseresolved wave dynamics and the consequential system response is crucial for real-time monitoring and control. A multi-variate, multi-step, long short term memory (MLSTM), a type of recurrent neural network (RNN) is used to capture complex system dynamics for real-time application. Results indicate that the integration of a wave prediction-reconstruction (WRP) model substantially enhances prediction accuracy by 50% on average relative to the baseline model. The improvement is consistent across various wave extremity and prediction horizons, thereby significantly broadening the scope for timely and precise predictive capabilities.

17 WIND ENERGY↗

Steepest-descent algorithm for simulating plasma-wave caustics via metaplectic geometrical optics

The design and optimization of radiofrequency-wave systems for fusion applications is often performed using ray-tracing codes, which rely on the geometrical-optics (GO) approximation. However, GO fails at wave cutoffs and caustics. To accurately model the wave behavior in these regions, more advanced and computationally expensive “full-wave” simulations are typically used, but this is not strictly necessary. A new generalized formulation called metaplectic geometrical optics (MGO) has been proposed that reinstates GO near caustics. The MGO framework yields an integral representation of the wavefield that must be evaluated numerically in general. We present an algorithm for computing these integrals using Gauss-Freud quadrature along the steepest-descent contours. Benchmarking is performed on the standard Airy problem, for which the exact solution is known analytically. Furthermore, the numerical MGO solution provided by the new algorithm agrees remarkably well with the exact solution and significantly improves on previously derived analytical approximations of the MGO integral.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

A Novel Zero-Discharge Supercritical Water-Based Wave Energy Desalination System

This paper presents a sustainable and innovative wave-energy-based water desalination system combined with an emerging supercritical water process for a zero-liquid-discharge technology. There is growing demand for producing clean water. Within desalination technologies, reverse osmosis, one of the most popular methods, uses a semipermeable membrane that separates fresh water from pressurized seawater. However, this technology produces brine, which is harmful to the environment. Supercritical water desalination is employed here as a means of using the brine to extract more fresh water and eliminate this environmentally toxic output. Wave energy is integrated with reverse osmosis to provide direct seawater pressurization for the first stage in the process. This wave energy converter converts the motion of waves into pressurized water through a power takeoff unit.

reverse osmosis↗

Mantaray: A Rust Package for Ray Tracing Ocean Surface Gravity Waves

Ocean surface gravity waves are an important component of air-sea interaction, influencing energy, momentum, and gas exchanges across the ocean-atmosphere interface. In specific applications such as refraction by ocean currents or bathymetry, ray tracing provides a computationally efficient way to gain insight into wave propagation. In this paper, we introduce Mantaray, an open-source software package implemented in Rust, with a Python interface, that solves the ray equations for ocean surface gravity waves. Mantaray is designed for performance, robustness, and ease of use. The package is modular to facilitate further development and can currently be applied to both idealized and realistic wave propagation problems (Fig. 1).

16 TIDAL AND WAVE POWER↗

Sensitivity to dark sector scales from gravitational wave signatures

We consider gravitational sound wave signals produced by a first-order phase transition in a theory with a generic renormalizable thermal effective potential of power law form. We find the frequency and amplitude of the gravitational wave signal can be related in a straightforward manner to the parameters of the thermal effective potential. This leads to a general conclusion; if the mass of the dark Higgs is less than 1% of the dark Higgs vacuum expectation value, then the gravitational wave signal will be unobservable at all upcoming and planned gravitational wave observatories. Although the understanding of gravitational wave production at cosmological phase transitions is still evolving, we expect this result to be robust.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Photoacoustic 3-D imaging of polycrystalline microstructure improved with transverse acoustic waves

Non-invasive fast imaging of grain microstructure of polycrystalline ceria with sub-micrometric spatial resolution is performed via time-domain Brillouin scattering. The propagation of a nanoacoustic pulse is monitored down to 8 µm deep in a 30 × 30 µm2 area. Grains boundaries are reconstructed in three-dimensions via a twostep processing method, relying on the wavelet synchro-squeezed transform and the alpha shape algorithm. Imaging contrast is improved by taking advantage of stronger sensitivity to anisotropy of transverse acoustic waves, compared with longitudinal waves. Utilization of transverse waves in the image processing reveals additional boundaries that are not discerned using longitudinal waves, confirmed by an electron backscattering diffraction pattern. A buried inclined interface between differently oriented grains is identified by monitoring changes in amplitude (phase) of the portion of the signal associated with transverse (longitudinal) waves. Estimates of the inclination angle of this interface prove the sensitivity of our laser ultrasonic method to image inclined boundaries.

36 MATERIALS SCIENCE↗

Topological d -wave superconductivity in two dimensions

Despite intensive searches for topological superconductors, the realization of topological superconductivity remains under debate. Previous proposals for the topological s-wave, p-wave, and chiral d-wave superconductivity have both advantages and disadvantages. In this review, we discuss two-dimensional topological superconductivity based on the non-chiral d-wave superconductors. It is shown that the noncentrosymmetric d-wave superconductors become topological superconductors under an infinitesimal Zeeman field without fine-tuning of parameters. Additionally, Floquet engineering for introducing the Zeeman field in a controllable way is also proposed. When the two-dimensional noncentrosymmetric superconductors are stacked to recover the global inversion symmetry, the field-induced parity transition may occur, and the high-field odd-parity superconducting state realizes various topological phases depending on the stacking structures. Two-dimensional heterostructures of strongly correlated electron systems, which have been developed by recent experiments, are proposed as a platform of the high-temperature topological superconductivity and the interplay of topology and strong correlations in superconductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Holistic Marine Energy Resource Assessments: A Wave and Offshore Wind Perspective of Metocean Conditions

Offshore wind and wave energy resources are possibly the last significantly untapped renewable energy resource, and could play a significant role in mitigating the worst impacts of climate change via the generation of renewable electricity. However, offshore wind and wave energy resource assessments have been conducted as independent parallel processes, with little interaction with regard to best practices, lessons learnt, or opportunities to create compatible methodologies for future utilization by the broader marine energy sector. Based on the latest technical specifications from the International Electrotechnical Commission, and the highest fidelity publicly available datasets, the offshore wind and wave conditions at the PacWave site off Oregon, USA were quantified. The results clearly show a significant untapped energy resource an annual average wave energy flux of ~35kW/m and a mean average wind speed of 7.8m/s. The offshore wind and wave energy resources both show significant seasonal variation, with offshore wind also featuring a consistent daily profile during summer. Finally, opportunities and challenges associated with developing a holistic assessment of offshore marine energy resources were discussed and recommendations provided.

Robertson, Bryson↗

Upper-Hybrid Waves Driven by Meandering Electrons Around Magnetic Reconnection X Line

Magnetic reconnection is a fundamental process in collisionless space plasma environment, and plasma waves relevant to the kinetic interactions can have a significant impact on the multiscale behavior of reconnection. Here, we present Magnetospheric Multiscale (MMS) observations during an encounter of an X line of symmetric magnetic reconnection in the magnetotail. The X line is characterized by reversals of ion and electron jets and electromagnetic fields, agyrotropic electron velocity distribution functions (VDFs), and an electron-scale current sheet. MMS observe large-amplitude nonlinear upper-hybrid (UH) waves on both sides of the neutral line, and the wave amplitudes have highly localized distribution along the normal direction. Here, the inbound meandering electrons drive the UH waves, releasing the free energy stored from the reconnection electric field along the meandering trajectories. The interaction between the meandering electrons and the UH waves may modify the balance of the reconnection electric field around the X line.

58 GEOSCIENCES↗

Seamless Projections of Global Storm Surge and Ocean Waves Under a Warming Climate

For coastal adaptation purposes, it is important to estimate the climate related changes in extreme sea levels due to storm surges and ocean waves, in addition to mean sea level rise. In this study, we provide the first consistent and continuous estimation of projected changes in global storm surges and ocean waves from the past to the warmer future, based on an extremely high resolution global climate model. The spatial pattern in the trend of annual maximum sea surface heights and wave heights is predominantly driven by changes in tropical cyclone (TC) frequency. In the western North Pacific, future TC frequencies are projected to decrease, and the annual maximum sea surface heights and wave heights show decreasing trends (-20 cm/century and -200 cm/century). Although highly intense tropical cyclones are enhanced in the warmer climate, highly extreme storm surges and wave heights do not necessarily increase due to the large natural variability.

54 ENVIRONMENTAL SCIENCES↗

On the Importance of Using Event-Specific Wave Diffusion Rates in Modeling Diffuse Electron Precipitation

A few to tens of keV electron precipitation that carries substantial energy source down to the upper atmosphere to create aurora is manifested as an important magnetosphere-ionosphere coupling process. The precipitation is usually caused by scattering processes associated with plasma waves in the magnetosphere. The scattering process is often quantified by wave diffusion rates that indicate how fast an electron is scattered. Global models commonly use diffusion coefficients that are derived from statistical wave models. However, due to the statistical nature, many localized, transient features could be smeared out. In this study, we investigate electron precipitation using event-specific diffusion coefficients that are obtained based on simultaneous in-situ measured/inferred, rather than statistical, chorus wave dynamics. We find that the application of the event-specific diffusion coefficients associated with a more dynamic and intense chorus wave model leads more electrons, particularly at several to tens of keV in the dawn-to-noon sector at L > 3, to precipitate than using statistical coefficients. Here, the new simulation roughly captures both the intensity and variability of the precipitating flux as detected by the NOAA/POES satellites. Ionospheric electron density in the lower E region (100–120 km) observed by the mid-latitude Millstone Hill radar is also much better reproduced, while the case using statistical diffusion coefficients underestimates the ionization rate. This study implies the importance of using event-specific diffusion rates in simulating the diffuse electron precipitation and understanding the magnetosphere-ionosphere coupling.

79 ASTRONOMY AND ASTROPHYSICS↗

Effects of EMIC Wave-Driven Proton Precipitation on the Ionosphere

In this report we investigate the proton precipitation caused by electromagnetic ion cyclotron (EMIC) waves and its impact on the ionosphere with the self-consistent ring current-atmosphere interactions model (RAM-SCBE) coupled with an ionospheric particle transport model Global Airglow (GLOW). The EMIC wave diffusion process causes significant precipitation of tens of keV protons, particularly in the afternoon to midnight sector. These precipitating energetic protons further impact the ionosphere-thermosphere and contribute to the ionization in the E/F regions. The integrated auroral conductance is significantly enhanced in the dusk-to-midnight sector. Although the EMIC waves do not directly interact with the ring current electrons, after the EMIC wave scattering included in the model, remarkable changes are found in the global distribution of precipitating electron flux. This means that the addition of proton precipitation driven by EMIC waves results in feedback effects on the ring current electron dynamics through the circulation system. Validation is also conducted by comparing the simulated precipitation flux and ionospheric electron density with observations.

79 ASTRONOMY AND ASTROPHYSICS↗

Magnetic Tilt Effect on Externally Driven Electromagnetic Ion Cyclotron (EMIC) Waves

Abstract We examine coupling of fluctuations in the solar wind with electromagnetic ion cyclotron (EMIC) waves in the magnetosphere using an advanced full‐wave simulation code, Petra‐M. Dipole tilt dramatically affects the coupling process. While very little wave power can reach the inner magnetosphere without tilt effects, a tilted dipole field dramatically increases the efficiency of the coupling process. Solar wind fluctuations incident at high magnetic latitude effectively reaches the ground along the field line and mode‐convert to linearly polarized field‐aligned propagating waves at the Alfvén and IIH resonances. Therefore, solar wind compressions efficiently drive linearly polarized EMIC waves when the dipole angle is tilted toward or away from the Sun‐Earth direction.

58 GEOSCIENCES↗

Wave and Particle Analysis of Z-Mode and O-Mode Emission in the Jovian Inner Magnetosphere

We report some of the most intense Z-mode and O-mode observations obtained by the Juno spacecraft while in orbit about Jupiter in a low to mid-latitude region near the inner edge of the Io torus. We have been able to estimate the density of the plasma in this region based on the lower frequency cutoff of the observed Z-mode emission. The results are compatible with the electron density measurements of the Jovian Auroral Distributions Experiment (JADE), on board the Juno spacecraft, if we account for unmeasured cold plasma. Direction-finding measurements indicate that the Z- and O-mode emission have distinct source regions. We have also used the measured phase space density of the JADE and the Jupiter energetic particle detector instruments to calculate estimated local growth rates of the observed O-mode and Z-mode emission assuming a loss cone instability and quasilinear analysis. The results suggest the emissions were observed near, but not within, a source region, and the free energy source is consistent with a loss cone. We have thus carried out the quasilinear wave analysis of the assumed remote Z- and O-mode wave growths. It is shown that the remotely generated waves, propagated through an inhomogeneous medium to the satellite location, may account for the observed wave characteristics. The importance of Z-mode in accelerating electrons in the inner Jovian magnetosphere makes these new wave mode confirmations at Jupiter of particular interest.

79 ASTRONOMY AND ASTROPHYSICS↗