A continuum of gravity waves in the Arecibo thermosphere?

Previous incoherent radar studies at Arecibo Observatory, Puerto Rico have demonstrated that ∼1–3% electron density “imprints” of internal gravity waves are routinely present in the Arecibo thermosphere (∼118–500 km). A special radar technique involving photoelectron‐enhanced plasma waves (PEPWs) was used for these observations. Recently, it was discovered that the trails of the gravity waves can be detected in standard incoherent scatter power profiles when properly filtered. This result was validated using simultaneous PEPW observations. This new development opens up the possibility of monitoring thermospheric gravity waves day and night. Preliminary studies indicate that gravity waves are continually propagating through the Arecibo thermosphere, and that “sets” of waves separated by approximately 20–60 min are typically present. With the aid of additional radar tests, it may be possible to unlock Arecibo power profiles recorded over the past 30 years for gravity wave studies. The precise origin of the waves is currently unknown.