Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
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A Localized Secular Variation Model of the Geomagnetic Field Over Northeast Asia Region between 1997 to 2011

지역화된 동북아시아지역의 지구자기장 영년변화 모델: 1997-2011

  • Kim, Hyung Rae (Dept. of Geoenvironmental Sciences, Kongju National Univ.)
  • 김형래 (공주대학교 지질환경과학과)
  • Received : 2014.12.27
  • Accepted : 2015.01.20
  • Published : 2015.02.28
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Abstract

I produced a secular variation model of geomagnetic field by using the magnetic component data from four geomagnetic observatories located in Northeast Asia during the years between 1997 and 2011. The Earth's magnetic field varies with time and location due to the dynamics of fluid outer core and the magnetic observatories on the surface measure in time series. To adequately represent the magnetic field or secular variations of the Earth, a spatio-temporal model is required. In making a global model, satellite observations as well as limited observatory data are necessary to cover the regions and time intervals. However, you need a considerable work and time to process a huge amount of the dataset with complicated signal separation procedures. When you update the model, the same amount of chores is demanded. Besides, the global model might be affected by the measurement errors of each observatory that are biased and the processing errors in satellite data so that the accuracy of the model would be degraded. In this study, as considered these problems, I introduced a localized method in modeling secular variation of the Earth's magnetic field over Northeast Asia region. Secular variation data from three Japanese observatories and one Chinese observatory that are all in the INTERMAGNET are implemented in the model valid between 1997 to 2011 with the interval of 6 months. With the resulting model, I compared with the global model called CHAOS-4, which includes the main, secular variation and secular acceleration models between 1997 to 2013 by using the three satellites' databases and INTERMAGNET observatory data. Also, the geomagnetic 'jerk' which is known as a sudden change in the time derivatives of the main field of the Earth, was discussed from the localized secular acceleration coefficients derived from spline models.

동북아시아에 위치한 4개의 지자기 관측소의 3성분 지구자기장 관측 자료를 이용하여 1997년부터 2011년 동안의 지구자기장의 영년변화를 표현하는 지역화된 영년변화 모델을 제작하였다. 외핵의 움직임으로 발생되는 지구자기장은 장소와 시간에 따라 변화하며 지자기 관측소에서는 이를 시계열로 측정하게 된다. 따라서 공간적인 변화를 함께 파악하기 위해서는 이를 시공간모델로 제작하여 시간에 따른 지구자기장의 변화를 공간적으로도 표현할 수 있도록 해야 한다. 전지구 범위인 경우 관측소의 분포가 제한되어 있고 이를 공간적으로 보완하기 위해 위성 자료를 활용한다. 하지만 방대하고 복잡한 위성 자료의 처리와 세계의 모든 지자기 관측소의 자료를 활용하여 전 지구적 지구자기장의 모델을 제작하는 일은 상당한 작업과 노력을 요구한다. 또한 계속해서 들어오는 자료들을 이용하여 모델을 업데이트 하는 일 역시 같은 양의 시간과 노력을 필요로 하게 된다. 더불어, 각 관측소 자료의 오차범위와 위성 자료 처리 오차 (processing error) 역시 지역에 따라 다르게 나타남으로 이러한 오차값들이 전지구 모델의 정확도에 영향을 미칠 수 있다. 본 논문에서는 이러한 문제점을 감안하여 동북아시아 지역을 중심으로 하는 지역화된(localized) 모델링 기법을 소개하고 이를 통해 지구자기장의 영년변화 모델을 제작하는 데 적용하였다. 전 세계의 지구자기장 관측망인 INTERMAGNET에 가입된 3개의 일본 관측소와 1곳의 중국 관측소 자료를 활용하여 1997년부터 2011년까지 6개월 간격으로 지구자기장의 변화를 파악하고 이를 전지구 모델과 비교해 보았다. 또한 얻어진 모델을 이용하여 지구 내부의 원인인 지구자기장의 급작스런 변화를 일컫는 지구자기장 '급변'을 찾아보고 이에 대한 발생 시기에 대해 논의하였다.

Keywords

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