• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.94-100
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• 2015

Coronal mass ejection (CME) released due to solar flare explosion cause geomagnetic disturbance. The induced current by massive geomagnetic disturbance can cause damage to the transformer. The calculated geoelectric field is a major parameter of the geomagnetically induced current (GIC). The method applying a Fourier transform has a high accuracy but it needs all data measured for 24 hours. And the other method applying a integral equation can calculate in real time but it requires to check an accuracy. To reduce the gap between the calculated results of two methods, it adjusts the integration section. As a result, the correlation between two calculated geoelectric fields is high, and the event time and direction of the calculated current is the same as that of the measured current, and it's accuracy rate is above 92 percent.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.11
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• pp.2562-2568
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• 2015

This paper proposes a detection method for irregularity of ionospheric delay in network RTK (Real Time Kinematic) Environment. The linearity of network RTK correction provided to user can't be assured when a characteristic of temporal-spatial of ionospheric delay is rapidly changed due to geomagnetic storm or solar flare. Therefore, incorrect ambiguity can be resolved and positioning error can be increased. A detection method for irregularity of ionospheric delay is needed to provide reliable correction. In this paper, index to detect irregularity of ionospheric delay is calculated from dispersive corrections and occurrence of irregularity is judged by comparing index and thresholds.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.45.2-46
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• 2020

Various processes, such as space weathering and granular convection, are occurring on asteroids' surfaces. Estimation of the surface exposure timescale is essential for understanding these processes. The Hayabusa mission target asteroid, (25143) Itokawa (Sq-type) is the only asteroid whose age is estimated from remote sensing observations as well as sample analyses in laboratories. There is, however, an unignorable discrepancy between the timescale derived from these different techniques. The ages estimated based on the solar flare track density and the weathered rim thickness of regolith samples range between 102 and 104 years [1][2]. On the contrary, the ages estimated from the crater size distributions and the spectra cover from 106 to 107 years [3][4]. It is important to notice that there is a common drawback of both age estimation methods. Since the evidence of regolith migration is found on the surface of Itokawa [5], the surficial particles would be rejuvenated by granular convection. At the same time, it is expected that the erasure of craters by regolith migration would affect the crater size distribution. We propose a new technique to estimate surface exposure age, focusing on the bright mottles on the large boulders. Our technique is less prone to the granular convection. These mottles are expected to be formed by impacts of mm to cm-sized interplanetary particles. Together with the well-known flux model of interplanetary dust particles (e.g., Grün, 1985 [6]), we have investigated the timescale to form such mottles before they become dark materials again by the space weathering. In this work, we used three AMICA (Asteroid Multi-band Imaging Camera) v-band images. These images were taken on 2005 November 12 during the close approach to the asteroid. As a result, we found the surface exposure timescales of these boulders are an order of 106 years. In this meeting, we will introduce our data analysis technique and evaluate the consistency among previous research for a better understanding of the evolution of this near-Earth asteroid.

• The Korean Journal of Air & Space Law and Policy
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• v.26 no.1
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• pp.241-269
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• 2011

Solar flare and storm may give an adverse effect upon electromagnetic environment around the Earth, so that various kinds of satellite cease to normally function. This kind of space storm disaster is characterized by the uncertainty about when and what size. Recently the UN has been paying attention to this plausible disaster. Particularly the COPUOS has taken the view that this disaster would threaten the sustainable space environment. The precautionary principle, rooted and excercised in the environment protection filed, has been adopted in the case of disaster with uncertainty. The reports and opinions given by the expert and representatives of the member States have stated that the precautionary principle should be adopted for the purpose of dealing with this disaster. On the other hand, it is advanced that the principle has been already included in the space law principle enshrined in the 1967 Space Treaty. The Treaty has adopted the freedom of navigation and use of the outer space for the interest of all States as the basic principles. Sustainable environment is necessary for implementing the principle. Therefore, the rules for the protection of sustainable space environment should be based upon the space law principle.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.431-440
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• 2005

Local K-index is an indicator representing local geomagnetic activity in every 3 hour. For estimation of the local K-index, a reasonable determination of solar quiet curve (undisturbed daily variation of geomagnetic field) is quiet essential. To derive the solar quiet curve, the FMI method, which is one of representative algorithms, uses horizontal components (H and D) of 3 days magnetometer data from the previous day to the next day for a specific day. However, this method is not applicable to real time forecast since it always requires the next day data. In this study, we have devised a new method to estimate local K-index in near real-time by modifying the FMI method. The new method selects a recent quiet day whose $K_p$ indices, reported by NOAA/SEC are all lower than 3, and replace the previous day and the next day data by the recent quiet day data. We estimated 2,672 local K indices from Gyeongzu magnetometer in 2003, and then compared the indices with those from the conventional FMI method. We also compared the K indices with those from Kakioka observatory. As a result, we found that (1) K indices from the new method are nearly consistent with those of the conventional FMI method with a very high correlation (R=0.96); (2) onr local K indices also have a relatively high correlation (R=0.81) with those from Kakioka station. Our results show that the new method can be used for near real-time estimation of local K indices from Gyeongzu magnetometer.