Rapidly fluctuating wind gusts blowing over mountains and hills can create "hotspots" high in the atmosphere and significantly affect regional air temperatures. A research paper to be published this month in the Journal of Geophysical Research-Space Physics reports that the actions of such winds can create high-frequency acoustic waves and could stimulate a 1000-Kelvin [1,000-degree Celsius; 2,000-degree Fahrenheit]spike in a short period of time in the thermosphere, at an altitude of 200-300 kilometers [100-200 miles]. Such exceptional temperature increases would require continuous waves, and the heating rate would likely be diminished with intermittent winds.
Richard Walterscheid and Michael Hickey used a theoretical model of the interaction between rough terrain and wind eddies to suggest that high winds may represent a previously unknown source of acoustic waves in the environment. Ocean waves and earthquakes are known to produce similar waves, which strengthen as they propagate higher in the atmosphere. The authors speculate that the waves can heat the atmosphere at prodigious rates and could account for a large part of the unusual and unexplained high-altitude background heating seen above the mountainous landscape in parts of South America.
"We show that that the acoustic waves generated by gusty flow over rough terrain might be a significant source of heating in the upper atmosphere," Hickey says. "These mysterious so-called hotspots observed above the Andes Mountains could be explained by such acoustic wave heating."
Harvey Leifert | EurekAlert!
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In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
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A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
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In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
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The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
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