Ionospheric response to the equatorial stratospheric wind

Abstract

Chen (1992) reports an association between the variance of the F2 layer critical frequency, foF2var, and the quasi-biennial oscillation, QBO, of the monthly mean zonal wind in the equatorial stratosphere (MMZW) at 40 mb, with data of March and September at Okinawa (26ºN, 128ºE). We search for such an association in other locations. Monthly-hourly foF2 data (between 12 and 19 LT) for the period 1957-1989 from Tucumán (27ºS; 65ºW), at the southern equatorial anomaly crest at the magnetic equator (Huancayo,12ºS; 75ºW), and in high latitude (Slough, 51ºN; 0.6ºW) were analyzed. The correlation coefficient between foF2var and MMZW is 0.05, 0.16 and 0.20 for Tucumán, Huancayo and Slough respectively, suggesting that there is no association. However, the correlation coefficient for Okinawa (r=0.65), and for Tucumán in the period 1958-1968 (r=0.67), is high. We do not rule out the possibility that the QBO of MMZW modulates the ionosphere at the crests of the equatorial anomaly. We look for an explanation of the loss of correlation for Tucumán after 1968. Spectral analysis, for all three stations, shows a significant highfrequency oscillation in foF2var (2.5-3.3 years) which is very close but not coincident with the QBO present in MMZW.