Forecasting the Occurrence of Ionospheric Scintillation Activity on a Day-to-Day Basis in the South American Sector

Details Forecasting the Occurrence of Ionospheric Scintillation Activity on a Day-to-Day Basis in the South American Sector Forecasting the Occurrence of Ionospheric Scintillation Activity on a Day-to-Day Basis in the South American Sector

May 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sa52c06a&link_type=abstract

American Geophysical Union, Spring Meeting 2001, abstract #SA52C-06

Computer Science

Sound

2411 Electric Fields (2712), 2415 Equatorial Ionosphere, 2439 Ionospheric Irregularities, 2447 Modeling And Forecasting

Scientific paper

In the low latitude ionospheric F region, ambient conditions after sunset are often conducive to the generation of small-scale plasma density structures by the Rayleigh-Taylor instability mechanism. Radio wave signals passing through these electron density irregularities experience amplitude fluctuations that lead to radio wave "scintillation". The scintillation index, S4, is a measure of the severity of these amplitude fluctuations. It is well known that the occurrence frequency of scintillation activity depends on solar cycle, season, longitude and local time, with a large day-to-day variability. In this paper, we present the results of a study that utilized a ground-based digital sounder at the magnetic equator to provide a "forecast" of the subsequent occurrence of scintillation activity and a network of UHF and L-band receivers that measured the S4 index, on a night-to-night basis. The observations were carried out in 1998 and 1999 in the Peruvian/Chilean longitude sector. The relationship between the magnitude of the vertical ExB drift velocity enhancement just after sunset as determined by the Jicamarca Digisonde and the magnitude of the S4 index observed by the scintillation receivers up to two hours later will be presented. In most cases at both UHF and L-band frequencies, this relationship is not linear, but there appears to be a "threshold" in ExB drift of ~ 20 m/sec. On nights when ExB drift was less than 20 m/sec, the UHF S4 index generally remained below 0.3 while on nights when ExB drift exceeded 20 m/sec, the S4 index was greater than 0.7. The day-to-day variability of this relationship will be presented and discussed.

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