New research sheds light on Solar Wind
December 11, 2007 New images and data from the Hinode space mission have provided a better understanding of the sun’s magnetic field and the origin of solar winds that blast through the solar system. Eruptions of magnetic energy from solar winds threaten satellites, telecommunications and electric power grids on Earth and a better understanding of the solar winds, which are propelled from the sun at speeds of almost one million miles per hour, could aid in the early prediction of damaging radiation waves before they reach satellites.
Hinode is a Japanese (JAXA) mission with NASA and Science and Technology Facilities Council (STFC) partnership and European Space Agency (ESA) participation which was launched in September 2006 to study the sun's magnetic field and how its explosive energy travels through the solar atmosphere. The Hinode spacecraft uses spectrometers that can view the Sun in optical, x-ray, and extreme ultraviolet wavelengths. Researchers have been able to capture images and video of structures and magnetic fields within the Sun’s plasma. The results (published in the 7 December issue of the journal Science) suggest magnetic waves - called Alfvén waves, play a critical role in driving solar wind into space.
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Until now it has been impossible to view Alfvén waves with the available instruments but Hinode allows researchers to capture high-resolution images and video showing structures and magnetic fields within the sun’s high-energy plasma. One research team used Hinode's high resolution x-ray telescope to look at x-ray jets (fountains of hot plasma) and observed a clear relationship between magnetic reconnection and the Alfvén wave formation. This led them to surmise that the number of x-ray jets and the high speeds of the outflowing plasma assist in the creation of fast solar wind.
Another team focused on the Sun's chromosphere, the region sandwiched between the solar surface and its corona and found it peppered with Alfvén waves. When the waves leak into the corona, they are strong enough to power the solar wind. They also discovered that, contrary to past models, Alfvén waves have periods of several minutes and occur when the sun's magnetic field is pushed around by convective motions and sound waves in the low atmosphere.
Data and images from Hinode should continue to provide researchers with insights into the effect of Alfvén waves on the solar world and could help to prevent satellite damage in the future.