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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/50426


    Title: An empirical model of the quiet daily geomagnetic field variation
    Authors: Yamazaki,Y;Yumoto,K;Cardinal,MG;Fraser,BJ;Hattori,P;Kakinami,Y;Liu,JY;Lynn,KJW;Marshall,R;McNamara,D;Nagatsuma,T;Nikiforov,VM;Otadoy,RE;Ruhimat,M;Shevtsov,BM;Shiokawa,K;Abe,S;Uozumi,T;Yoshikawa,A
    Contributors: 太空科學研究所
    Keywords: EQUIVALENT CURRENT SYSTEMS;NORTH-AMERICAN LOCATIONS;SQ CURRENT SYSTEM;IONOSPHERIC CURRENTS;SOLAR-CYCLE;EQUATORIAL ELECTROJET;SEMIANNUAL VARIATIONS;SEASONAL-VARIATIONS;DYNAMO CURRENTS;LOW LATITUDES
    Date: 2011
    Issue Date: 2012-03-27 17:31:35 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 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.
    Relation: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
    Appears in Collections:[太空科學研究所 ] 期刊論文

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