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