TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 62 (No. 4), pp. e9-e12, 2010


First sequential images of the plasmasphere from the meridian perspective observed by KAGUYA

Go Murakami1, Ichiro Yoshikawa1, Yuki Obana1, Kazuo Yoshioka1, Gentaro Ogawa1, Atsushi Yamazaki2, Masato Kagitani3, Makoto Taguchi4, Masayuki Kikuchi5, Shingo Kameda2, and Masato Nakamura2

1Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
2Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
3Planetary Plasma and Atmospheric Research Center, Tohoku University, Aramaki-aza-aoba, Aoba, Sendai 980-8578, Japan
4Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
5National Institute of Polar Research, 10-3, Midoricho, Tachikawa, Tokyo 190-8518, Japan

(Received December 18, 2009; Revised January 24, 2010; Accepted February 20, 2010; Online published March 26, 2010)

Abstract: Our understanding of plasmaspheric dynamics has increased in recent years largely due to the information generated during the IMAGE-EUV mission. Even though this successful mission has ended, we have succeeded in imaging the terrestrial helium ions (He+) by the Telescope of Extreme Ultraviolet (TEX) aboard the Japanese lunar orbiter KAGUYA by detecting resonantly scattered emission at 30.4 nm. The view afforded by the KAGUYA orbit encompasses the plasma (He+) distribution in a single exposure, enabling us to examine for the first time the globally averaged properties of the plasmasphere from the ``side" (meridian) perspective. The TEX instrument observed a medium-scale density structure in the dawnside plasmasphere during a quiet period (1-2 June 2008). The meridian shape of the structure clearly agreed with the dipole magnetic field line. The TEX instrument also observed the structure in the plasmasphere co-rotating with a duration of 26 h, which is consistent with results from a number of recent studies derived from the IMAGE-EUV mission. These results confirm that the TEX instrument successfully obtained the spatial distribution and temporal variation of the plasmasphere.
Key words: Plasmasphere, EUV, KAGUYA, corotation.

Corresponding author E-mail: go@eps.s.u-tokyo.ac.jp

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