Tuesday, January 1, 2008
Science Update - A look at CfA discoveries from recent journals

The Hinode (Japanese for "sunrise") satellite was launched last September to study the sun's magnetic field, and how its explosive energy propagates through the different layers of the solar atmosphere.
One of the three instruments on board Hinode is the X-Ray Telescope (XRT), developed and built by the SAO and the Japan Aerospace Exploration Agency. The sun's hot corona and magnetic fields power eruptions that hurl gases and energetic charged particles upwards. The particles reaching the earth can disrupt communications, cause power line surges, and create other disturbances.

The December 7 issue of Science magazine features the first results from Hinode; the issue's cover picture is of the sun taken with XRT. The journal contains five peer-reviewed articles on Hinode coauthored by SAO scientists, among a set of Hinode articles that the editors describe as providing "important clues to the mechanisms heating the corona and the acceleration of the solar wind."

In one of these articles, SAO astronomers Edward DeLuca, Loraine Lundquist, Jay bookbinder, Leon Golub, Kelly Korreck, and Yingna Su, along with fifteen of their Japanese colleagues, address the fundamental issue of the origin of the solar wind. Scientists neither understand where the wind originates on the sun's surface, nor how the wind is accelerated towards the planets after it leaves the sun's surface. The XRT observed active, X-ray emitting regions on the sun continuously for three days, with its highest spatial resolution. They discovered adjacent to an active sunspot a region with hot, outflowing gas moving with velocities of about 140 kilometers per second, and with enough material in it to supply about one quarter of the typical solar wind. When they compared their images with earlier solar studies of magnetic fields (to which the authors had also contributed), they found a close positional correspondence with magnetic fields that open into space rather than loop back down to the surface. The results imply that a significant portion of the solar wind (perhaps all of its slower components) arise in the boundary zones of these active regions.