The Gem Infrasound Logger: A Lightweight, Low-Power, Low-Cost, Open-Source Infrasound Logger

Low-frequency acoustic waves (called infrasound) are used for monitoring atmospheric disturbances including nuclear tests, volcanoes, and other powerful phenomena. Brief but focused infrasound campaigns enable the study of a wide range of sites and phenomena at low cost and with few workers. However, the cost, weight, and general inconvenience of commercial data loggers has limited past infrasound campaigns. To solve this problem, I developed an Arduino-based infrasound logger (the Gem) with a fraction of the cost, weight, and installation time. The Gem has since been adopted by several institutions for infrasound recording at volcanoes, stratospheric balloons, and river rapids

Volcano Infrasound: Progress and Future Directions

Over the past two decades (2000–2020), volcano infrasound (acoustic waves with frequencies less than 20 Hz propagating in the atmosphere) has evolved from an area of academic research to a useful monitoring tool. As a result, infrasound is routinely used by volcano observatories around the world to detect, locate, and characterize volcanic activity. It is particularly useful in confirming subaerial activity and monitoring remote eruptions, and it has shown promise in forecasting paroxysmal activity at open-vent systems. Fundamental research on volcano infrasound is providing substantial new insights on eruption dynamics and volcanic processes and will continue to do so over the next decade. The increased availability of infrasound sensors will expand observations of varied eruption styles, and the associated increase in data volume will make machine learning workflows more feasible. More sophisticated modeling will be applied to examine infrasound source and propagation effects from local to global distances, leading to improved infrasound-derived estimates of eruption properties. Future work will use infrasound to detect, locate, and characterize moving flows, such as pyroclastic density currents, lahars, rockfalls, lava flows, and avalanches. Infrasound observations will be further integrated with other data streams, such as seismic, ground- and satellite-based thermal and visual imagery, geodetic, lightning, and gas data. The volcano infrasound community should continue efforts to make data and codes accessible and to improve diversity, equity, and inclusion in the field. In summary, the next decade of volcano infrasound research will continue to advance our understanding of complex volcano processes through increased data availability, sensor technologies, enhanced modeling capabilities, and novel data analysis methods that will improve hazard detection and mitigation

Whitewater Sound Dependence on Discharge and Wave Configuration at an Adjustable Wave Feature

Stream acoustics has been proposed as a means of monitoring discharge and wave hazards from outside the stream channel. To better understand the dependence of sound on discharge and wave characteristics, this study analyzes discharge and infrasound data from an artificial wave feature which is adjusted to accommodate daily changes in recreational use and seasonal changes in irrigation demand. Monitorable sound is only observed when discharge exceeds ∼35 m3/s, and even above that threshold the sound-discharge relationship is non-linear and inconsistent. When sound is observed, it shows consistent dependence on wave type within a given year, but the direction of this dependence varies among the 3 years studied (2016, 2021, and 2022). These findings support previous research that establishes discharge and stream morphology as relevant controls on stream acoustics and highlights the complex, combined effects of these variables

Acoustic and Seismic Fields of Hydraulic Jumps at Varying Froude Numbers

Mechanisms that produce seismic and acoustic wavefields near rivers are poorly understood because of a lack of observations relating temporally dependent river conditions to the near-river seismoacoustic fields. This controlled study at the Harry W. Morrison Dam (HWMD) on the Boise River, Idaho, explores how temporal variation in fluvial systems affects surrounding acoustic and seismic fields. Adjusting the configuration of the HWMD changed the river bathymetry and therefore the form of the standing wave below the dam. The HWMD was adjusted to generate four distinct wave regimes that were parameterized through their dimensionless Froude numbers (Fr) and observations of the ambient seismic and acoustic wavefields at the study site. To generate detectable and coherent signals, a standing wave must exceed a threshold Fr value of 1.7, where a nonbreaking undular jump turns into a breaking weak hydraulic jump. Hydrodynamic processes may partially control the spectral content of the seismic and acoustic energies. Furthermore, spectra related to reproducible wave conditions can be used to calibrate and verify fluvial seismic and acoustic models

The effect of the regular solution model in the condensation of protoplanetary dust

We utilize a chemical equilibrium code in order to study the condensation process which occurs in protoplanetary discs during the formation of the first solids. The model specifically focuses on the thermodynamic behaviour on the solid species assuming the regular solution model. For each solution, we establish the relationship between the activity of the species, the composition and the temperature using experimental data from the literature. We then apply the Gibbs free energy minimization method and study the resulting condensation sequence for a range of temperatures and pressures within a protoplanetary disc. Our results using the regular solution model show that grains condense over a large temperature range and therefore throughout a large portion of the disc. In the high temperature region (T > 1400 K) Ca-Al compounds dominate and the formation of corundum is sensitive to the pressure. The mid-temperature region is dominated by Fe(s) and silicates such as Mg2SiO4 and MgSiO3 . The chemistry of forsterite and enstatite are strictly related, and our simulations show a sequence of forsterite-enstatite-forsterite with decreasing temperature. In the low temperature regions (T < 600 K) a range of iron compounds and sulfides form. We also run simulations using the ideal solution model and see clear differences in the resulting condensation sequences with changing solution model In particular, we find that the turning point in which forsterite replaces enstatite in the low temperature region is sensitive to the solution model. Our results show that the ideal solution model is often a poor approximation to experimental data at most temperatures important in protoplanetary discs. We find some important differences in the resulting condensation sequences when using the regular solution model, and suggest that this model should provide a more realistic condensation sequence.Comment: MNRAS: Accepted 2011 February 16. Received 2011 February 14; in original form 2010 July 2

Robust optical delay lines via topological protection

Phenomena associated with topological properties of physical systems are naturally robust against perturbations. This robustness is exemplified by quantized conductance and edge state transport in the quantum Hall and quantum spin Hall effects. Here we show how exploiting topological properties of optical systems can be used to implement robust photonic devices. We demonstrate how quantum spin Hall Hamiltonians can be created with linear optical elements using a network of coupled resonator optical waveguides (CROW) in two dimensions. We find that key features of quantum Hall systems, including the characteristic Hofstadter butterfly and robust edge state transport, can be obtained in such systems. As a specific application, we show that the topological protection can be used to dramatically improve the performance of optical delay lines and to overcome limitations related to disorder in photonic technologies.Comment: 9 pages, 5 figures + 12 pages of supplementary informatio