What are energetic neutral atoms?
Energetic Neutral Atoms (ENAs) are particles with no charge that move relatively fast. ENAs are formed from particles that are ionized, meaning they have lost electrons. Sometimes, these ions interact with neutral atoms taking the electrons from those neutral atoms and becoming neutral themselves. Since the particle is no longer charged (it has equal numbers of protons and electrons) it no longer reacts to the magnetic fields, and travels in a straight line from the spot where the interaction occurred.
This interaction is called charge exchange. Charge exchange can happen between solar wind ions and neutral atoms from the Interstellar Medium. Some of these ENAs happen to travel in just the right way so that they enter the IBEX spacecraft for collection. There are so many energetic particles that interact with interstellar neutrals, that even though they could travel in any direction, the IBEX sensors are able to pick up between 1 per hour and a few per minute.
About the Boundary of the Solar System
|
