TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 64 (No. 6), pp. 417-423, 2012

Long-term behavior of annual and semi-annual Sq variations

Yosuke Yamazaki1 and Kiyohumi Yumoto1,2

1Department of Earth and Planetary Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
2Space Environment Research Center, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan

(Received April 12, 2010; Revised January 24, 2011; Accepted January 31, 2011; Online published July 27, 2012)

Abstract: We have examined the long-term behavior (solar-cycle time scale) of annual and semi-annual Sq variations. We analyzed geomagnetic data observed at locations that were roughly geographically conjugate in the west Pacific region (Kakioka and Gnangara) during the last five solar cycles (1953-2006). Three-year compound data were constructed for each station for each year. The stationary component 0, annual component 1, and the semi-annual component 2, of the Sq variations were derived from the compound data. The solar-activity dependence of the derived three components was evaluated in comparison with the sunspot number (). It was found that the amplitudes of all three components (0, 1 and 2) have a positive linear correlation with the sunspot number. The most remarkable result is that the linear regression coefficient for 0 is much bigger than those of 1 and 2. The physical mechanisms involved are yet to be understood.
Key words: Sq, ionosphere, ionospheric current, ionospheric conductivity, solar activity, sunspot number, geomagnetism, geomagnetic field.

Corresponding author E-mail: zaki@geo.kyushu-u.ac.jp

[Full text] (PDF 2.3 MB)