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Science 7 December 2007:
Vol. 318. no. 5856, pp. 1585 - 1588
DOI: 10.1126/science.1147292
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Reports

Continuous Plasma Outflows from the Edge of a Solar Active Region as a Possible Source of Solar Wind

Taro Sakao,1* Ryouhei Kano,2 Noriyuki Narukage,1 Jun'ichi Kotoku,2 Takamasa Bando,2 Edward E. DeLuca,3 Loraine L. Lundquist,3 Saku Tsuneta,2 Louise K. Harra,4 Yukio Katsukawa,2 Masahito Kubo,5 Hirohisa Hara,2 Keiichi Matsuzaki,1 Masumi Shimojo,6 Jay A. Bookbinder,3 Leon Golub,3 Kelly E. Korreck,3 Yingna Su,3 Kiyoto Shibasaki,6 Toshifumi Shimizu,1 Ichiro Nakatani1

The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray–emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to ~1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.

1 Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229–8510, Japan.
2 National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181–8588, Japan.
3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138, USA.
4 University College London (UCL)–Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey RH56NT, UK.
5 High Altitude Observatory, National Center for Atmospheric Research (NCAR), Post Office Box 3000, Boulder, CO 80307–3000, USA.
6 Nobeyama Radio Observatory, NAOJ, 462-2 Nobeyama, Minamimaki, Minamisaku, Nagano 384–1305, Japan.

* To whom correspondence should be addressed. E-mail: sakao{at}solar.isas.jaxa.jp

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Are There Alfven Waves in the Solar Atmosphere?.
R. Erdelyi and V. Fedun (2007)
Science 318, 1572-1574
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Science. ISSN 0036-8075 (print), 1095-9203 (online)