HR: 1330h
AN: SA12B-1097    [PDF]
TI: A Continuum of Gravity Waves in the Arecibo Thermosphere?
AU: * Djuth, F T
EM: djuth@ix.netcom.com
AF: Geospace Research, Inc., 550 N. Continental Blvd., El Segundo, CA 90245 United States
AU: Sulzer, M P
EM: msulzer@naic.edu
AF: National Astronomy and Ionosphere Center, Arecibo Observatory, Arecibo, PR 00612 United States
AU: Gonzalez, S A
EM: sixto@naic.edu
AF: National Astronomy and Ionosphere Center, Arecibo Observatory, Arecibo, PR 00612 United States
AU: Elder, J H
EM: John@JElder.com
AF: Geospace Research, Inc., 550 N. Continental Blvd., El Segundo, CA 90245 United States
AB: Previous radar studies conducted at Arecibo Observatory, Puerto Rico [e.g., Djuth et al., Radio Sci., 32, 2321-2344, 1997] have demonstrated that $\sim$1-3% electron density "imprints" of internal gravity waves are routinely observed in the Arecibo thermosphere ($\sim$118 km - 400 km). A special radar technique involving photoelectron-enhanced plasma waves (PEPWs) was used for these observations. The imprints are decisively detected at 30-60 standard deviations above the "noise level" imposed by the measurement technique. In general, the observed electron density imprints are relatively "clean" in that their vertical wavelength spectrum is characteristically narrow-banded. This technique is effective only during the daytime when large fluxes of photoelectrons are present in the Arecibo ionosphere. On average, good observing conditions exist for about 7 hours a day. The limited diurnal coverage is arguably the greatest shortcoming of the technique. Recently, it was discovered that the trails of these waves can be detected in standard incoherent scatter power profiles when properly filtered. This result was validated using simultaneous PEPW observations. The new development opens up the possibility of monitoring thermospheric gravity waves day and night. Preliminary studies indicate that "sets" of gravity waves separated by approximately 30-60 minutes are continually propagating through the Arecibo thermosphere, at least during the daytime when most of the current data is available. With the aid of additional radar tests, it may be possible to unlock power profiles recorded over the past 30 years at Arecibo for gravity wave studies. Possible sources of the thermospheric gravity waves include ocean waves or reconstituted waves arising from nonlinear wave processes in the mesosphere. However, the exact origin of the waves is currently not well-settled.
DE: 0358 Thermosphere--energy deposition
DE: 2443 Midlatitude ionosphere
DE: 2494 Instruments and techniques
DE: 6952 Radar atmospheric physics
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting