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Science 7 December 2007:
Vol. 318. no. 5856, pp. 1580 - 1582
DOI: 10.1126/science.1147050
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Reports

Evidence for Alfvén Waves in Solar X-ray Jets

J. W. Cirtain,1,2* L. Golub,1 L. Lundquist,1 A. van Ballegooijen,1 A. Savcheva,1 M. Shimojo,3 E. DeLuca,1 S. Tsuneta,4 T. Sakao,5 K. Reeves,1 M. Weber,1 R. Kano,4 N. Narukage,5 K. Shibasaki3

Coronal magnetic fields are dynamic, and field lines may misalign, reassemble, and release energy by means of magnetic reconnection. Giant releases may generate solar flares and coronal mass ejections and, on a smaller scale, produce x-ray jets. Hinode observations of polar coronal holes reveal that x-ray jets have two distinct velocities: one near the Alfvén speed (~800 kilometers per second) and another near the sound speed (200 kilometers per second). Many more jets were seen than have been reported previously; we detected an average of 10 events per hour up to these speeds, whereas previous observations documented only a handful per day with lower average speeds of 200 kilometers per second. The x-ray jets are about 2 x 103 to 2 x 104 kilometers wide and 1 x 105 kilometers long and last from 100 to 2500 seconds. The large number of events, coupled with the high velocities of the apparent outflows, indicates that the jets may contribute to the high-speed solar wind.

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.
2 Marshall Space Flight Center, National Aeronautics and Space Administration (NASA) VP62, Huntsville, AL 35812, USA.
3 Nobeyama Solar Radio Observatory, Nobeyama, Nagano 384–1305, Japan.
4 National Astronomical Observatory of Japan (NAOJ), Mitaka, Tokyo 181–8588, Japan.
5 Institute of Space and Astronautical Science, (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa 229–8510, Japan.

* To whom correspondence should be addressed. E-mail: Jonathan.W.Cirtain{at}nasa.gov

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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R. Erdelyi and V. Fedun (2007)
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