• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.67-73
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• 2009

The changes of geomagnetic flux density distribution on the ground surface by underground empty spaces had been investigated through the variations of the soil density and measuring heights. The geomagnetic flux density distributions were monitored for the surfaces of different density, sink-hole and tunnel by fluxgate-type magnetometer. The underground empty space and low soil density decreased the geomagnetic flux densities, which were decreased from the boundary of raw and low-density (empty) grounds, and showed the lowest value at the center of low-density (empty) ground. The decreases of geomagnetic flux density by underground empty spaces could be found at the surface with the tunnel located at 80 m underground. And, the underground defects of empty spaces, low density zone, fracture zone and sink holes could be monitored by the phenomena of this decreasing flux density.

• Journal of Astronomy and Space Sciences
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• v.29 no.4
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• pp.329-336
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• 2012

Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Bohyunsan Observatory to measure the Earth's magnetic field variations in South Korea. In 2007, we installed a fluxgate magnetometer (RFP-523C) to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we use the H, D, Z components of fluxgate magnetometer data to investigate the characteristics of mid-latitude geomagnetic field variation. To remove the temporary changes in Earth's geomagnetic filed by space weather, we use the international quiet days' data only. In other words, we performed a superposed epoch analysis using five days per each month during 2008-2011. We find that daily variations of H, D, and Z shows similar tendency compared to previous results using all days. That is, H, D, Z all three components' quiet intervals terminate near the sunrise and shows maximum 2-3 hours after the culmination and the quiet interval start from near the sunset. Seasonal variations show similar dependences to the Sun. As it becomes hot season, the geomagnetic field variation's amplitude becomes large and the quiet interval becomes shortened. It is well-known that these variations are effects of Sq current system in the Earth's atmosphere. We confirm that the typical mid-latitude geomagnetic field variations due to the Sq current system by excluding all possible association with the space weather.

• Korean Journal of Remote Sensing
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• v.30 no.2
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• pp.259-274
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• 2014

On Aug 18, 2013, Sakurajima volcano in Japan erupted on a relatively large-scale. Geostationary Ocean Color Imager (GOCI) had used to detect volcanic ash in the surrounding area on the next day of this eruption. The geomagnetic variation has been analyzed using geomagnetic data from Cheongyang observatory in Korea and several geomagnetic observatories in Japan. First, we reconstruct geomagnetic data by principal component analysis and conduct semblance analysis by wavelet transform. Secondly, we minimize the error of solar effect by using wavelet based semblance filtering with Kp index. As a result of this study, we could confirm that the geomagnetic variation usually occur at the moment of Sakurajima volcano eruption. However, we cannot rule out the possibilities that it could have been impacted by other factors besides volcanic eruption in other variation's cases. This research is an exceptional study to analyze geomagnetic variation related with abroad volcanic eruption uncommonly in Korea. Moreover, we expect that it can help to develop further study of geomagnetic variation involved in earthquake and volcanic eruption.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.131-135
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• 2006

The objective of the project is to model and study the geomagnetic field structure and its secular variation in space and in time due to sources in the dynamic fluid outer core. the Earth's spherical harmonic model of the main field and of the secular variation gives the intensity and geomagnetic structure at any location around the Earth, assuming an undistorted, steady state field that no external sources or localized earth anomalies. To consider the practical use of a ship's digital compass in Earth's magnetic field, Earth's spherical harmonic model is searched for the related practical methods and procedures as a basic study in this work.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.319-327
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• 2010

We examine the ionospheric F2-layer electron density variation by solar activity in middle latitude by using foF2 observed at the Kokubunji ionosonde station in Japan for the period from 1997 to 2008. The semi-annual variation of foF2 shows obviously in high solar activity (2000-2002) than low solar activity (2006-2008). It seems that variation of geomagnetic activity by solar activity influences on the semi-annual variation of the ionospheric F2-layer electron density. According to the Lomb-Scargle periodogram analysis of foF2 and Ap index, interplanetary magnetic field (IMF) Bs (IMF Bz <0) component, solar wind speed, solar wind number density and flow pressure which influence the geomagnetic activity, we examine how the geomagnetic activity affects the ionospheric F2-layer electron density variation. We find that the semi-annual variation of daily foF2, Ap index and IMF Bs appear clearly during the high solar activity. It suggests that the semi-annual variation of geomagnetic activity, caused by Russell-McPherron effect, contributes greatly to the ionospheric F2-layer semi-annual electron density variation, except dynamical effects in the thermosphere.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.06a
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• pp.103-113
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• 2004

We investigate the time-variational characteristics of power spectrum and transfer function of geomagnetic field by robust estimation technique. In the case of power spectrums of geomagnetic field, there are some the periodic fluctuations related with solar activity, Meanwhile, the geomagnetic transfer function shows so considerable weak time-variational fluctuation that the estimations of transfer function seem to be comparatively stable in time-variant view.

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.93-93
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• 2004

We have examined the solar wind dynamic pressure enhancements during geomagnetic storm main phase. The Dst index has been used to identify more than 100 geomagnetic storms which occurred in the time interval of 1997 to 2001. We have selected only the events having the minimum Dst value less than -50 nT. In order to identify the pressure impact, we have looked at the low latitude ground H data as well as the solar wind pressure data themselves. (omitted)

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.9 no.1
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• pp.1-15
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• 1991

This paper is to aim to review the basic theory of geomagnetic survey and analize the field observation data (1980-1989) measured by Korea G S I. The magnetic Chart of Korea is mapped with use of the analized results and the principal scheme about Korea geomagnetic survey is furthermore proposed

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.27.2-27.2
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• 2011

The Total Electron Content (TEC) measured from Global Positioning System (GPS) can be continuously or peculiarly increased (positive ionospheric storm) or decreased (negative ionospheric storm) with solar and geomagnetic activities as well as the chemical and dynamic processes with thermosphere in the mid-latitudes. The ionospheric storm is not easy to predict owing to its difficult mechanism, and the real-time GPS TEC monitoring may be useful to follow ionospheric response to solar and geomagnetic storms. Korea Astronomy & Space Science Institute has continuously monitor GPS TEC over Korea Peninsula in near real-time of 10 minutes to watch activities. In this presentation, we will report the variation of GPS TEC over Daejeon and JeJu in Korea during the period of solar flare eruption and geomagnetic storm events in 2011. These events in 2011 will be compared with the event in October 2003 and November 2004.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.1
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• pp.19-25
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• 2017

Recently, indoor LBS has been attracting much attention because of its promising prospect. One of key technologies for its success is indoor location estimation. A popular one for indoor positioning is to find the location based on the strength of received Wi-Fi signals. Since the Wi-Fi services are currently prevalent, it can perform indoor positioning without any further infrastructure. However, it is found that its accuracy depends heavily on the surrounding radio environment. To alleviate this difficulty, we present a novel indoor position technique employing the geomagnetic characteristics as well as Wi-Fi signals. The geomagnetic characteristic is known to vary according to the location. Therefore, employing the geomagnetic signal in addition to Wi-Fi signals is expected to improve the location estimation accuracy.