An empirical model of the quiet daily geomagnetic field variation

作者：Yamazaki Y^*; Yumoto K; Cardinal M G; Fraser B J; Hattori P; Kakinami Y; Liu J Y; Lynn K J W; Marshall R; McNamara D; Nagatsuma T; Nikiforov V M; Otadoy R E; Ruhimat M; Shevtsov B M; Shiokawa K; Abe S; Uozumi T; Yoshikawa A

来源：Journal of Geophysical Research, 2011, 116: A10312.

DOI：10.1029/2011JA016487

An empirical model of the quiet daily geomagnetic field variation has been constructed based on geomagnetic data obtained from 21 stations along the 210 Magnetic Meridian of the Circum-pan Pacific Magnetometer Network (CPMN) from 1996 to 2007. Using the least squares fitting method for geomagnetically quiet days (Kp <= 2+), the quiet daily geomagnetic field variation at each station was described as a function of solar activity SA, day of year DOY, lunar age LA, and local time LT. After interpolation in latitude, the model can describe solar-activity dependence and seasonal dependence of solar quiet daily variations (S) and lunar quiet daily variations (L). We performed a spherical harmonic analysis (SHA) on these S and L variations to examine average characteristics of the equivalent external current systems. We found three particularly noteworthy results. First, the total current intensity of the S current system is largely controlled by solar activity while its focus position is not significantly affected by solar activity. Second, we found that seasonal variations of the S current intensity exhibit north-south asymmetry; the current intensity of the northern vortex shows a prominent annual variation while the southern vortex shows a clear semi-annual variation as well as annual variation. Thirdly, we found that the total intensity of the L current system changes depending on solar activity and season; seasonal variations of the L current intensity show an enhancement during the December solstice, independent of the level of solar activity.

• 出版日期2011-10-18
• 单位中央民族大学