Remote Sensing Infrasound using a “Space Microphone”

  • CART Astrophysics Seminar Series

April 23, 2026 2:00 PM - April 23, 2026 3:00 PM
PAIS 3205

Host:
Diana Dragomir
Presenter:
Ken Obenberger (AFRL)
Earth’s mesosphere and lower thermosphere (MLT) are often collectively referred to as the ignorosphere because measurements are difficult to come by. Balloons cannot fly above ~40 km altitude and satellites typically do not fly below ~200 km (unless they are on fire). Fortunately, the MLT coincides with the ionosphere (iMLT), where plasma interacts with radio frequencies (RF). These RF-plasma interactions allows for remote sensing from ground systems such as high frequency (HF; 3-30 MHz) radars or global navigation satellite systems (GNSS). One area of interest for ionospheric remote sensing is in the detection of atmospheric waves. Despite this region being considered “space” there is still enough atmosphere to allow for the propagation of acoustic waves and gravity waves (not gravitational waves!) generated by energetic tropospheric events such as tsunamis, earthquakes, thunderstorms, or anthropogenic explosions. These waves couple to the ionospheric ions and produce a signature on RF remote sensing systems. I will review the physics of these sources, the atmospheric waves they create, and how we can detect them using ground-based instruments. I will also highlight a recent experiment carried out in Socorro New Mexico as part of the DARPA Atmosense program, where we successfully detected 10 explosions using an ionospheric radar network.  

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