Journal of the Korean earth science society (한국지구과학회지)

The Korean Earth Science Society (한국지구과학회)
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On the Temporal Variability of Geomagnetic Field and Transfer Function at Icheon Observatory

이천관측소에서 측정된 지자기장 및 지자기 전달함수의 시간적 변동성

  • Lee, Duk-Kee (Marine Meteorology & Earthquake Res. Lab., Meteorological Research Institute) ;
  • Kwon, Byung-Doo (Department of Earth Science Education, Seoul National University) ;
  • Youn, Yong-Hoon (Marine Meteorology & Earthquake Res. Lab., Meteorological Research Institute) ;
  • Yang, Jun-Mo (Marine Meteorology & Earthquake Res. Lab., Meteorological Research Institute)
  • 이덕기 (기상연구소 해양기상지진연구실) ;
  • 권병두 (서울대학교 지구과학교육과) ;
  • 윤용훈 (기상연구소 해양기상지진연구실) ;
  • 양준모 (기상연구소 해양기상지진연구실)
  • Published : 2004.10.30
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Abstract

Using three-components geomagnetic data from a permanent geomagnetic observatory in Icheon, we have computed the power spectrum of each geomagnetic component, amplitude, phase and estimation error of transfer function for each day in the 6 months period July 2002${\sim}$December 2002. The temporal variation of power spectrum have random appearances with repeating relative strong and weak magnitude, which is considered as solar activities. However, there is no clear long-term trend. In the case of amplitude, phase and error of transfer function, even though there are some random patterns over the periods of 1000 s and under 100 s, they seem to be comparatively stable without manifest temporal changes. Futhermore, we have estimated electrical field by assuming P$_{1}\;^{0}$ spherical harmonics and then calculated the approximated apparent resistivity for each day. As a result, the variations of resistivity depend on the temporal magnitude of spectral power in horizontal magnetic fields rather than hydrological changes in near surface.

경기도 이천에서 2002년 7월부터 12까지 총 6개월 동안 측정된 지자기 3성분 자료를 이용하여 일별 각 성분의 스펙트럼, 지자기 전달함수의 크기, 위상, 오차 등을 계산하였다. 지자기 스펙트럼은 관측기간 동안 태양활동에 의한 무작위적 강약이 반복되는 형태를 보여주었고, 유의미한 시간적 변동은 존대하지 않았다. 지자기 전달함수의 크기, 위상, 오차의 경우, 주기 100초 이하와 주기 1000초 이상에서 부분적으로 무작위적인 경향을 확인할 수 있었으나, 시간에 따른 증감추세 없이 대체로 안정적인 값을 보였다. 이와 더불어, 전기장의 P$_{1}\;^{0}$ 소스(zonal harmonics) 가정을 통하여 시간에 따른 근사적인 겉보기 전기비저항의 변동을 조사하였는데, 근사된 전기비저항의 변화는 지각의 자체적인 물성 변화보다는 수평 자기장 성분의 시간적 강약에 지배적임을 확인할 수 있었다.

Keywords

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