HEA Research: Solar Wind X-rays

The solar wind originates in the million-degree solar corona and flows out from the sun at a million miles per hour. Most of the ions in the wind are hydrogen and helium, but a small fraction are heavier elements such as carbon, oxygen, and neon. When those heavy ions collide with neutral gas in comets, planetary atmospheres, or very tenuous gas throughout the solar system, they emit X-rays via a process called charge exchange. Many comets and planets have been observed using X-ray telescopes. There is also a diffuse X-ray glow from the Earth's outer atmosphere and from the entire solar system as the solar wind streams out to the edges of the heliosphere, well beyond Pluto. Wherever our X-ray telescopes point, they look through this geocoronal and heliospheric glow. The Local Origin X-rays (LOX) group is a collaboration of CfA and other scientists to observe and model this emission. Charge exchange spectra are also studied in an ongoing laboratory research program.



HEA Brad Wargelin, Richard Edgar, Michael Juda, Paul Plucinsky, Jonathan Slavin
AMP Alexander Dalgarno, Vasili Kharchenko
SSP John Raymond


X-ray Image of the Moon. This image was taken by ROSAT in June of 1990 when the Moon was about half-full. X-rays on the bright side are from solar fluorescence of the lunar surface. There is also some faint emission that appears on the dark side. Chandra's observations of the Moon a decade later showed that the dark-side X-rays are actually coming from the Earth's outer atmosphere, as solar wind ions charge exchange with Earth's very tenuous envelope of H gas. Learn more...
Image Credit: ROSAT/J. Schmitt et al.


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