The coronagraph is an instrument that enables the investigation of faint features in the vicinity of the Sun, particularly coronal mass ejections (CMEs). So far coronagraphic observations have been mainly used to determine the geometric and kinematic parameters of CMEs. Here, we introduce a new method for the determination of CME temperature using a two filter (4025 °A and 3934 °A) coronagraph system. The thermal motion of free electrons in CMEs broadens the absorption lines in the optical spectra that are produced by the Thomson scattering of visible light originating in the photosphere, which affects the intensity ratio at two different wavelengths. Thus the CME temperature can be inferred from the intensity ratio measured by the two filter coronagraph system. We demonstrate the method by invoking the graduated cylindrical shell (GCS) model for the 3-dimensional CME density distribution and discuss its significance.

Abstract
1. INTRODUCTION
2. METHOD AND RESULT
3. DISCUSSION
REFERENCES

• Kyuhyoun Cho(Department of Physics and Astronomy, Seoul National University) Corresponding author
• Jongchul Chae(Department of Physics and Astronomy, Seoul National University)
• Eun-kyung Lim(Korea Astronomy and Space Science Institute)
• Kyung-suk Cho(Korea Astronomy and Space Science Institute/University of Science and Technology)
• Su-Chan Bong(Korea Astronomy and Space Science Institute/University of Science and Technology)
• Heesu Yang(Department of Physics and Astronomy, Seoul National University)