Source of solar wind found
An international team of astronomers has located the precise source on the Sun of the high speed solar winds emanating from it. The results are published in the latest issue of Science. The search for the source of the solar wind has been like the hunt for the source of the Nile," said Don Hassler of the Southwest Research Institute, Boulder, Colorado, lead author of the paper in Science. For 30 years, scientists have observed high speed solar wind coming from regions in the solar atmosphere with open magnetic field lines, called coronal holes. However, only recently have we been able to measure the detailed structure of this source region".
The nature and origin of the solar wind is one of the main mysteries which the Solar and Heliospheric Observatory (SOHO), a joint project of the American and the European space agencies, was designed to solve. The solar wind is a high speed stream of electrically charged gas flowing from the surface of the Sun. It comes in two varieties: high speed and low speed. The low speed solar wind moves at roughly 400 kilometers per second, while the high speed wind is even faster, moving at speeds as high as 800 km/s. It has long been thought that the solar wind flows from coronal holes; what is new is the discovery that these outflows are concentrated in specific patches at the edges of the honey-comb shaped magnetic fields. Just below the surface of the Sun there are large convection cells, and each cell has a magnetic field associated with it.
If one thinks of these cells as paving stones in a patio, then the solar wind is breaking through like grass around the edges, concentrated in the corners where the paving stones meet", said Dr. Helen Mason, University of Cambridge, England, and co-author of the paper to appear in Science. However, at speeds ranging from 8 km/s at the surface to over 800 km/s, the solar wind 'grows' much faster than grass".
As it flows past Earth, the solar wind changes the shape and structure of the Earth's magnetic field. In the past, the solar wind did not directly affect us, but as the human race become increasingly dependent on advanced technology, it becomes more susceptible to its effects. Researchers are learning that variations in the solar wind flow can cause dramatic changes in the shape of the Earth's magnetic field, which can damage satellites and disrupt communications and power systems.