What is black aurora?
Gaps between diffuse aurora. Sometimes you can have diffuse auroral curtains and arcs that have small gaps. These gaps are usually thinner than the arc thickness next to the gap, and they look like a black auroral curtain embedded in the bright auroral glow around them. The black auroras can have curls and other structure. The sense of direction of these curls is opposite to that of regular auroral curtains. Most likely, the electric fields that are present in the upper ionosphere or lower magnetosphere prevent electrons from reaching the atmosphere, or even turn precipitating electrons around.
