Energetic neutral atom Energetic neutral atom 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.
Diffusion damping scattering decreased dramatically. Scattering less, photons could diffuse (travel) much greater distances. There was no significant diffusion damping for electrons, which could not diffuse nearly as far as photons could in similar circumstances. Thus all damping by electron diffusion is negligible when compared to photon diffusion damping. Acoustic perturbations of initial density fluctuations in the universe made some regions of space hotter and denser than others. These differences in temperature and density are called "anisotropies". Photons diffused from the hot, overdense regions of plasma to the cold, underdense ones: they dragged along the protons and electrons: the photons pushed electrons