Energetic neutral atoms

Energetic neutral atom (ENA) imaging, often described as "seeing with atoms", is a technology used to create global images of otherwise invisible phenomena in the magnetospheres of planets and throughout the heliosphere, even to its outer boundary. This constitutes the far-flung edge of the solar system.

The solar wind consists of ripped-apart atoms (called plasma) flying out of the Sun. This is mostly hydrogen, that is, bare electrons and protons, with a little bit of other kinds of nuclei, mostly helium. The space between solar systems is similar, but they come from other stars in our galaxy. These charged particles can be redirected by magnetic fields; for instance, Earth's magnetic field shields us from these particles. But, every so often, a few of them steal electrons from neutral atoms they run into. At that point, they become neutral, although they're still moving very fast, and they travel in an exact straight line. These are called Energetic Neutral Atoms. ENA images are constructed from the detection of these energetic neutral atoms.

Earth's magnetosphere preserves Earth's atmosphere and protects us from cell-damaging radiation. This region of "space weather" is the site of geomagnetic storms that disrupt communications systems and pose radiation hazards to humans traveling at high polar altitudes or in orbiting spacecraft. A deeper understanding of this region is vitally important. Geomagnetic weather systems have been late to benefit from the satellite imagery taken for granted in weather forecasting, and space physics because their origins in magnetospheric plasmas present the added problem of invisibility.

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