X-rays from the Sun
Credit: ISAS/Yohkoh team/Lockheed Palo Alto Research Laboratory

Soft X-ray emission from the Sun

The outer part of the Sun's atmosphere is a churning cauldron of hot gas, heated by magnetic processes which originate in the solar interior. The gas in the outermost part of the solar atmosphere (the solar "corona") gets heated to millions of degrees, and is an abundant source of soft X-rays. The X-ray emission from the solar corona is a measure of the amount of heat in the outer solar atmosphere, and a measure of the magnetic activity in the sun's interior. The image above shows the soft X-ray emission from the solar corona; dark regions are regions of little X-ray emission, while brighter regions show parts of the sun where X-ray production is abundant. Note that the emission is not uniform around the sun, and that a large fraction of the bright emission is in the form of "loops" anchored in the solar surface and extending into space. The image above was obtained on November 23, 1999 by the Soft X-ray Telescope, on board the Japanese satellite Yohkoh ("sunbeam") . The Yohkoh mission is a Japanese solar observatory (with US and UK participation) which was launched on August 31, 1991. Yohkoh is designed to answer many questions about the physics of the solar corona and solar flares. The Japanese Institute for Space and Astronautical Sciences (ISAS) provides overall program management, the launch vehicle, the mission instruments, and a Wide Band Spectrometer. The Soft X-ray Telescope was designed by the Lockheed Palo Alto Research Laboratory, under NASA support, in collaboration with the National Astronomical Observatory of Japan and the University of Tokyo. Yohkoh has become a vital tool for observing and attempting to understand solar flares.

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Page Author: Dr. Michael F. Corcoran
Last modified February 15, 2002