1. Solar and Space Weather Research Group, Korea Astronomy and Space Science Institute, Daejeon 305-348, South Korea
2. Department of Astronomy and Space Science, University of Science and Technology, Daejeon, South Korea
3. Department of Physics, Pohang University of Science and Technology, Pohang 790-784, South Korea
4. School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701, South Korea
5. Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA