VHF Observations of Small-scale Ionosphere TEC Fluctuations with an Astronomical Interferometer

Details VHF Observations of Small-scale Ionosphere TEC Fluctuations with an Astronomical Interferometer VHF Observations of Small-scale Ionosphere TEC Fluctuations with an Astronomical Interferometer

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsa51e..06h&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SA51E-06

Other

[2435] Ionosphere / Ionospheric Disturbances, [2437] Ionosphere / Ionospheric Dynamics, [2439] Ionosphere / Ionospheric Irregularities

Scientific paper

We have used a relatively long, contiguous VHF observation of a bright astronomical radio source (Cygnus A) with the Very Large Array (VLA) to demonstrate the capability of this instrument and others like it to observe and study ionosphere density fluctuations on scales much smaller than is possible with other instruments. We have shown that with a bright source, the VLA can detect fluctuations in total electron content (TEC) with amplitudes of only 0.001 TECU and in some cases, even lower. The VLA easily detected and tracked traveling ionospheric disturbances (TIDs) which were seen to begin around dusk, persist for about 3-4 hours, and move preferentially northward. We were also able to detect a different class of wave-like disturbances with pattern speeds ranging from roughly 20-220 m/s with no apparent preferred direction of motion which are present throughout the night. The data suggest that for these smaller waves, at any given time, no one wave is dominant and that the VLA is likely observing many waves at once. We also find evidence of a persistent set of phenomena which are isotropic and are comparable in size with the VLA (likely <20 km). These phenomena produce extremely small fluctuations of about 0.003 TECU and may be moving rather fast (up to ~500 m/s). We have also begun to expand this project to include similar observations of Cygnus A and other bright sources in the VLA data archives. Preliminary results confirm the utility of the VLA VHF system to continue to explore the transient phenomena previously observed through other times of day and year. In particular, we have found instances of ionospheric scintillation which, while much larger in amplitude, closely resemble the detected 0.003 TECU fluctuations in spatial and temporal scale.

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