What is proton aurora?
A diffuse auroral glow caused by precipitating energetic protons, usually too dark to be visible. Most visible aurora comes from precipitating electrons. However, the magnetosphere also shoots energetic protons toward the atmosphere. Both electrons and protons are charged particles, and they are not free to move in just any direction (see question 6). The curtain shapes of aurora results from this restriction on the motion of charged particles. When an electron spirals along the magnetic field into the atmosphere, it stays on or near this field line even when it makes a collision. Therefore the aurora looks like rays or curtains. When a proton spirals into the atmosphere along a field line it is just as restricted in its motion. In a collision, however, the proton can catch an electron from the atom or molecule that it collides with, and it is then a neutral hydrogen atom (i.e. a proton and an electron bound together). This hydrogen atom is free to travel in any direction, independent
