Unexplained what? Wikipedia would go a very long way toward explaining much of that "unexplainable".
Just a couple, off the top of my head:
Sprites and jets are electrical discharges, like lightning, except they point up, not down.
"The Sirius Mystery", I presume, refers to Sirius being called a red star in some ancient Egyptian document. The only time the Egyptians were deeply interested in Sirius was when it rose before the Sun to signal the time for the Nile to flood. When celestial objects are near a clear horizon, they often look red: witness the Sun or the Moon. Sirius is no different - its blue light gets scattered nore than its red. So a "red Sirius" was what the Egyptians were looking for. The every-night white Sirius that was high in the southern sky was visible over half the year. A red Sirius before sunrise was
important!