Computer Science – Sound
Scientific paper
May 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agusmsa21a..01w&link_type=abstract
American Geophysical Union, Spring Meeting 2005, abstract #SA21A-01
Computer Science
Sound
2400 Ionosphere, 2435 Ionospheric Disturbances, 2437 Ionospheric Dynamics, 2439 Ionospheric Irregularities, 2494 Instruments And Techniques
Scientific paper
The manifestation of atmospheric gravity waves (AGWs) in the ionosphere is called a traveling ionospheric disturbance (TID). TIDs can be thought of as traveling corrugations in the ionosphere, and as such can seriously affect HF radio communications and surveillance systems. They may indirectly play a greater role in disrupting communications by triggering the growth of ionospheric instabilities, resulting in scintillation of radio signals. It is therefore of great interest to monitor TIDs on a routine basis, and to correlate their properties with other phenomena. In this paper, we present data from a unique radio technique for measuring TID properties such as their spectrum, and their spectrally resolved propagation characteristics. One of the most sensitive methods for detecting transient changes in the ionosphere is the HF Doppler technique operating in the 3-10 MHz band. HF Doppler systems have advantages over all other techniques for the measurement of TID characteristics. They are more amenable to analysis than data from ionosonde chains, and their time resolution (30 sec) is much higher than that of ionosondes . Unlike total electron content (TEC) methods, which respond to height-integrated TID effects, the HF Doppler radar responds to TIDs at the altitude of the radio reflection point. Finally, HF Doppler systems have low power consumption, so that both spatial and temporal resolution can be maintained for many days without the costs that would be associated with an incoherent-scatter radar. SwRI recently designed, built and deployed an HF Doppler sounding system in Texas, to investigate TIDs. The TIDDBIT radar consisted of three transmitters (Austin, Uvalde and St. Hedwig) and a receiver in San Antonio, Texas. Using a cross-spectral analysis technique, TID speeds and azimuths were obtained for each wave frequency. We provide a synoptic survey of the TID characteristics observed over Texas during January-March 2002. The Doppler system provides an accurate measure of both the TID and AGW periods, and the TID velocities are also an accurate estimate of the underlying gravity wave horizontal and vertical trace velocities. Such a system could be usefully deployed to monitor the properties of bottomside F-region undulations that are thought to trigger ionospheric instabilities in low latitude regions.
Bronn J. S.
Crowley Geoff
Fessler B. W.
Wene Gregory Peter
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