On the quasi-biennial oscillation (QBO) signal in the foF2 ionospheric parameter

The presence of the quasi-biennial oscillation (QBO) signal in the ionospheric foF2 parameter is investigated using several ionosonde stations. From data continuity, 22 ground-based stations were selected, covering a latitudinal range from 77 degrees S to 74 degrees N. Monthly average data were filtered using a wavelet multi-resolution method and the data in the band corresponding to the QBO signal (16-32 months) were searched with an iterative regression method to find periodicities. Significant periods in that band were found in 13 stations. A QBO-related signal is found in all latitudes and most periods are within 25-29 months. The amplitude of QBO is typically 0.15-0.20 (foF2), which is similar to 10% of the solar cycle signal. Thus the existence of a QBO-type variation in ionosphere was confirmed. Nevertheless, the present analysis does not permit one to conclude if the cause of this variation is related to the solar-geomagnetic QBO, to the stratospheric QBO or to both. (c) 2006 Elsevier Ltd. All rights reserved.