Earth Planets Space, Vol. 62 (No. 1), pp. 57-61, 2010
Hiroshi Kobayashi1,2, Hiroshi Kimura1,3, Satoru Yamamoto4,5, Sei-ichiro Watanabe6, and Tetsuo Yamamoto1
1Institute of Low Temperature Science, Hokkaido University, Kita-ku Kita-19 Nisi-8, Sapporo 060-0819, Japan
2Astrophysical Institute and University Observatory, Friedrich Schiller University Jena, Schillergaesschen 2-3, 07745 Jena, Germany
3Center for Planetary Science, Graduate School of Science, Kobe University, Nada-ku Rokkodai-cho 1-1, Kobe 657-8501, Japan
4Graduate school of frontier science, Univ. of Tokyo, Kashiwanoha 5-1-5, Kashiwa 277-8562, Japan
5National institute for environmental studies, Onogawa 16-2, Tsukuba 305-8506, Japan
6Department of Earth and Planetary Sciences, Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
(Received September 4, 2008; Revised February 26, 2009; Accepted March 12, 2009; Online published February 12, 2010)
The flux of interplanetary dust beyond the Jupiter's orbit, which supposedly originates from Edgeworth-Kuiper belt, has been measured in situ by instruments on board Voyager and Pioneer spacecraft. The measured flux shows a nearly flat radial profile at 10-50 AU for Voyager and at 5-15 AU for Pioneer. Because the orbital evolution of dust particles controlled by radiation forces results in the flux that is inversely proportional to distance from the sun, dust particles detected by spacecraft should have suffered from other dynamical effects. We calculate model fluxes on the spacecraft taking into account the effect of ice sublimation as well as radiation forces on the orbital evolution of dust particles. Our results show that the radial profile of the model flux becomes relatively flat near the outer edge of the sublimation zone, where ice substantially sublimes. The expected location of the flat radial profile, which depends on the detection threshold of instruments, is 15-40 AU for Voyager and 5-20 AU for Pioneer. Because our model fluxes are comparable with the measured ones, we conclude that the flat radial profiles of the dust flux derived from in-situ dust impacts may be caused by ice sublimation.
Key words: Ice sublimation, Edgeworth-Kuiper belt, solar system, dust.