Multiple resolution surface wave tomography: the Mediterranean basin

From a large set of fundamental-mode surface wave phase velocity observations, we map the transversely isotropic lateral heterogeneities in the upper-mantle shear velocity structure. We design a multiple resolution inversion procedure, which allows us to parametrize any selected region more finely than the rest of the globe. We choose, as a high-resolution region, the upper mantle underlying the Mediterranean basin. We formulate the inverse problem as in a previous paper by Boschi & Ekström, calculating regional JWKB (Jeffreys-Wentzel-Kramers-Brillouin) surface wave sensitivity kernels for each pixel of a 2°× 2° starting model, including the high-resolution global crustal map Crust 2.0. We find that the available surface wave data can resolve the most important geophysical features of the region of interest, providing a reliable image of intermediate spatial wavelengt

First-principles calculations of the lattice thermal conductivity of the lower mantle

The temperature variations on top of the core-mantle boundary are governed by the thermal conductivity of the minerals that comprise the overlying mantle. Estimates of the thermal conductivity of the most abundant phase, MgSiO3 perovskite, at core-mantle boundary conditions vary by a factor of ten. We performed ab initio simulations to determine the lattice thermal conductivity of MgSiO3 perovskite, finding a value of 6.8 ± 0.9 W m-1 K-1 at core-mantle boundary conditions (136 GPa and 4000 K), consistent with geophysical constraints for the thermal state at the base of the mantle. Thermal conductivity depends strongly on pressure, explaining the dynamical stability of super-plumes. The dependence on temperature and composition is weak in the deep mantle: our results exhibit saturation as the phonon mean free path approaches the interatomic spacing. Combining our results with seismic tomography, we find large lateral variations in the heat-flux from the core that have important implications for core dynamics

2022 Review of Data-Driven Plasma Science

Data-driven science and technology offer transformative tools and methods to science. This review article highlights the latest development and progress in the interdisciplinary field of data-driven plasma science (DDPS), i.e., plasma science whose progress is driven strongly by data and data analyses. Plasma is considered to be the most ubiquitous form of observable matter in the universe. Data associated with plasmas can, therefore, cover extremely large spatial and temporal scales, and often provide essential information for other scientific disciplines. Thanks to the latest technological developments, plasma experiments, observations, and computation now produce a large amount of data that can no longer be analyzed or interpreted manually. This trend now necessitates a highly sophisticated use of high-performance computers for data analyses, making artificial intelligence and machine learning vital components of DDPS. This article contains seven primary sections, in addition to the introduction and summary. Following an overview of fundamental data-driven science, five other sections cover widely studied topics of plasma science and technologies, i.e., basic plasma physics and laboratory experiments, magnetic confinement fusion, inertial confinement fusion and high-energy-density physics, space and astronomical plasmas, and plasma technologies for industrial and other applications. The final section before the summary discusses plasma-related databases that could significantly contribute to DDPS. Each primary section starts with a brief introduction to the topic, discusses the state-of-the-art developments in the use of data and/or data-scientific approaches, and presents the summary and outlook. Despite the recent impressive signs of progress, the DDPS is still in its infancy. This article attempts to offer a broad perspective on the development of this field and identify where further innovations are required

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Multiple resolution surface wave tomography: the Mediterranean basin

From a large set of fundamental-mode surface wave phase velocity observations, we map the transversely isotropic lateral heterogeneities in the upper-mantle shear velocity structure. We design a multiple resolution inversion procedure, which allows us to parametrize any selected region more finely than the rest of the globe. We choose, as a high-resolution region, the upper mantle underlying the Mediterranean basin. We formulate the inverse problem as in a previous paper by Boschi & Ekstrom, calculating regional JWKB (Jeffreys-Wentzel-Kramers-Brillouin) surface wave sensitivity kernels for each pixel of a 2degrees x 2degrees starting model, including the high-resolution global crustal map Crust 2.0. We find that the available surface wave data can resolve the most important geophysical features of the region of interest, providing a reliable image of intermediate spatial wavelength. RI Ekstrom, Goran/C-9771-201

Seismic Structure of the Upper Mantle Beneath Eastern Asia From Full Waveform Seismic Tomography

To better understand the subsurface behavior of subducting slabs and their relation to the tectonic evolution of the overriding plate, we conduct a full waveform inversion on a large data set to determine a high‐resolution seismic model, FWEA18 (Full Waveform inversion of East Asia in 2018), of the upper mantle beneath eastern Asia. FWEA18 reveals sharper, more intense high‐velocity slabs in the upper mantle under the southern Kuril, Japan, and Ryukyu arcs, than previous studies have found. The subducting Pacific plate is imaged as a roughly 100 km thick high‐velocity slab to near 550 km depth indicating relatively little deformation. Stagnation near 600 km depth is observed over horizontal distances of 600 km or less. The Pacific plate we image accounts for roughly 25 Myr of subduction with older slab likely located in the lower mantle. The Philippine plate, subducting beneath the Ryukyu Islands, has a clear termination at about 450 km depth. This may indicate a tearing event in the past or that less Philippine Sea plate has subducted than previously thought. We found a double‐layer high‐velocity anomaly above and below 660 km under the Yellow Sea and eastern coast of North China. This may correspond to parts of the Philippine Sea plate that detached in the past and Pacific plate that have intersected at depth or a complicated behavior of the Pacific plate at that depth. Slow cylindrical anomalies cross the entire upper mantle are imaged beneath major Holocene volcanoes, which are likely upwellings associated with the edges of deep slabs that are entering the lower mantle