- Title
- An empirical model of the quiet daily geomagnetic field variation
- Creator
- Yamazaki, Y.; Yumoto, K.; Nagatsuma, T.; Nikiforov, V. M.; Otadoy, R. E.; Ruhimat, M.; Shevtsov, B. M.; Shiokawa, K.; Abe, S.; Uozumi, T.; Yoshikawa, A.; Cardinal, M. G.; Fraser, B. J.; Hattori, P.; Kakinami, Y.; Liu, J. Y.; Lynn, K. J. W.; Marshall, R.; McNamara, D.
- Relation
- Journal of Geophysical Research: Space Physics Vol. 116, Issue A10, p. 1-21
- Publisher Link
- http://dx.doi.org/10.1029/2011ja016487
- Publisher
- American Geophysical Union
- Resource Type
- journal article
- Date
- 2011
- Description
- 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.
- Subject
- 210 MM; L current system; MAGDAS/CPMN; Sq current system; empirical model; ionosphere
- Identifier
- http://hdl.handle.net/1959.13/1056018
- Identifier
- uon:15977
- Identifier
- ISSN:0148-0227
- Language
- eng
- Full Text
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