In recent years, ultrasonic methods have been developed that can be used to measure the mechanical stiffness of materials.1-5 In one such method, the velocity of a flexural plate wave, the lowest order antisymmetric Lamb mode, is measured as a function of frequency. Lamb waves arise from a coupling at the free boundaries between the shear waves and compressional waves in a plate structure.6 The...

In the course of the energization of electrons to energies of some tens of keV during the impulsive phase of a solar flare, the velocity distribution function of the electrons is predicted to become anisotropic with T e ‖ > T e ⊥ (Here, ‖ and ⊥ denote directions with respect to the background magnetic field). Such a configuration can become unstable to the so-called Electron Firehose instabilit...

Recent observations of polar plumes in the southern solar coronal hole by the Extreme-Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft show signatures of quasi-periodic compressional waves with periods of 10È15 minutes. The relative wave amplitude was found to increase with height in the plumes up to about 1.2 Using a one-dimensional linear wave equation for the magnetosonic R _...

Inversion of 4036 P wave travel time residuals from 429 local earthquakes using a tomographic scheme provides information about three-dimensional upper crustal velocity variations in the Indian Wells Valley-Coso region of southeastern California. The residuals are calculated relative to a Coso-specific velocity model, corrected for station elevation, weighted, and back-projected along their ray...

SUMMARY The geophysical detection of magma bodies and the estimation dimensions, physical properties volume fraction each phase composing is required to improve forecasting volcanic hazards understand transcrustal magmatism. We develop an analytical model calculate P waves velocity in a three-phase consisting crystals gas bubbles suspended viscous melt. apply our speed sound as function tempera...

Poroelasticity theory predicts wave velocities in a saturated porous medium through coupling between the bulk deformation of solid skeleton and fluid flow. The challenge emerges below characteristic wavelengths at which hydrodynamic interactions grains pore become important. We investigate pressure volume fraction dependence compressional- shear-wave fluid-saturated, random, isotropic, friction...

A compilation of 54 sets of geoacoustic measurements of marine sediments was reviewed in order to bound estimates of parameters for use in Buckingham's grain shearing (GS) theory of acoustic propagation. These data, for unconsolidated sands (siliciclastic and carbonate) with grain sizes between 0.0156 mm and 0.57 mm, were all made in shallow water (maximum depth of 60 m) sites at diverse locale...

S U M M A R Y We present a derivation of the equations describing wave propagation in porous media based upon an averaging technique which accommodates the transition from the microscopic to the macroscopic scale. We demonstrate that the governing macroscopic equations determined by Biot remain valid for media with gradients in porosity. In such media, the well-known expression for the change i...