“The height of the ionosphere/space transition is controlled in part by the amount of extreme ultraviolet energy emitted by the Sun and a somewhat contracted ionosphere could have been expected because C/NOFS was launched during a minimum in the 11-year cycle of solar activity.”
I seem to recall some Russian guy saying how there are regions of increased energy in the Universe and our entire solar system passes through them at times. I believe he says (or perhaps the data proves) that we are passing through one of these Universal Energy Zones (or whatever they call them) now. So not just the Sun’s energy perhaps.