Outflow structure of the quiet sun corona probed by spacecraft radio scintillations in strong scattering

Journal Article · Fri Jun 20 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/788/2/117· OSTI ID:22356613

Imamura, Takeshi; Ando, Hiroki; Toda, Tomoaki; Nakamura, Masato ^[1]; Tokumaru, Munetoshi; Shiota, Daikou ^[2]; Isobe, Hiroaki; Asai, Ayumi ^[3]; Miyamoto, Mayu ^[4]; Häusler, Bernd ^[5]; Pätzold, Martin ^[6]; Nabatov, Alexander ^[7]; Yaji, Kentaro ^[8]; Yamada, Manabu ^[9]

---

1. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
2. Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 484-8601 (Japan)
3. Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471, Japan. (Japan)
4. Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
5. Institut für Raumfahrttechnik, Universität der Bundeswehr München, D-85577 Neubiberg (Germany)
6. Rheinisches Institut für Umweltforschung, Department Planetenforschung, Universität zu Köln, Aachener Strasse 209, D-50931 Köln (Germany)
7. The Institute of Radio Astronomy, National Academy of Science of Ukraine, Chervonoprapornaya, Strasse 4, Kharkov 61002 (Ukraine)
8. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
9. Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba 275-0016 (Japan)

Radio scintillation observations have been unable to probe flow speeds in the low corona where the scattering of radio waves is exceedingly strong. Here we estimate outflow speeds continuously from the vicinity of the Sun to the outer corona (heliocentric distances of 1.5-20.5 solar radii) by applying the strong scattering theory to radio scintillations for the first time, using the Akatsuki spacecraft as the radio source. Small, nonzero outflow speeds were observed over a wide latitudinal range in the quiet-Sun low corona, suggesting that the supply of plasma from closed loops to the solar wind occurs over an extended area. The existence of power-law density fluctuations down to the scale of 100 m was suggested, which is indicative of well-developed turbulence which can play a key role in heating the corona. At higher altitudes, a rapid acceleration typical of radial open fields is observed, and the temperatures derived from the speed profile show a distinct maximum in the outer corona. This study opened up a possibility of observing detailed flow structures near the Sun from a vast amount of existing interplanetary scintillation data.

• OSTI ID: 22356613
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 788; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
ALTITUDE
AVAILABILITY
DENSITY
DISTANCE
FLUCTUATIONS
PLASMA
PROBES
RADIOWAVE RADIATION
SCATTERING
SCINTILLATIONS
SOLAR WIND
SUN
TURBULENCE
VELOCITY