Abstract Thermospheric waves occurring around the time of the 14 July 2000 solar flare were investigated using the Global Ionosphere and Thermosphere Model. The simulation results showed that extensive acoustic and gravity waves were excited by the solar flare in the subsolar region. The subsolar buoyancy period at 400 km altitude was approximately 16 min. Gravity waves with frequencies lower t...

A monopole or a dipole source in a fluid borehole generates acoustic waves, part of which propagate along the borehole and the other part enter the formation propagating as Por S-waves. The refracted waves propagating along the borehole wall are used to determine Pand S-wave velocities. However, a significant fraction of the seismic energy radiates into the formation. In this laboratory study, ...

An experimental and theoretical investigation of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material has been made. Particular attention was paid to the phenomenon of acoustic streaming of the liquid in the porous material due to the damping of the acoustic waves. The experiments were performed on Berea sandstone cores. Two acoustic horns were used w...

The transfer behavior of acoustic waves at a sudden change in cross section in a duct system is investigated. In particular, a method is presented which allows to determine the coefficients of transmission and reflection of plane acoustic waves by combining large eddy simulation (LES) of turbulent compressible flow with system identification. The complex aeroacoustic interactions between acoust...

Bubbles confined in microchannels self-organize without directly contacting one another when excited by an external acoustic field. The bubbles tend to form periodic "crystal"-like lattices with a finite interbubble distance. This equilibrium distance can be adjusted by simply tuning the acoustic frequency. This new type of crystal is purely mediated by acoustic surface waves emitted by the pul...

We study the effect of a violation of the strong equivalence principle (SEP) on the cosmic microwave background (CMB). Such a violation would modify the weight of baryons in the primordial gravitational potentials and hence their impact in the establishment of the photon-baryon plasma acoustic oscillations before recombination. This cosmolog-ical Nordtvedt effect alters the odd peaks height of ...

An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrat...

A new instability mechanism is described in accretion flows where the gas is accelerated from a stationary shock to a sonic surface. The instability is based on a cycle of acoustic and entropic waves in this subsonic region of the flow. When advected adiabatically inward, entropy perturbations trigger acoustic waves propagating outward. If a shock is present at the outer boundary, acoustic wave...

The linewidth of longitudinal acoustic waves in densified silica glass is obtained by inelastic x-ray scattering. It increases with a high power alpha of the frequency up to a crossover where the waves experience strong scattering. We find that alpha is at least 4, and probably larger. Resonance and hybridization of acoustic waves with the boson-peak modes seems to be a more likely explanation ...