Basics about sightings of Aurora Borealis also known as Northern- or polar lights, in middle latitudes

 KP index*: Roughly speaking, auroras can already be observed visually from KP 5-6 (G1/2 storm) in northern Germany. At KP 7/8 (G3/4 storm) or above also in southern Germany (Alps to southern Europe). Among other things, the density and speed of the flares or CME's (earth directed solar mass ejection forms) or corona holes are relevant parameters for the strength of the solar storms and visual sightings. But the Bz value which definite the north- south  alignment of the earth magnetic field ( May 2024, Bz -50nT ) is the most important factor. If this Bz value is to weak, the protons can't invade in the earth magnetic field. By the way, the glowing phenomenon is triggered by 'animated' oxygen and nitrogen atoms. Oxygen up to ~100 km shows greenish colors and from ~100-200 km red to orange.  Nitrogen atoms up  to ~300 km shows more seldom purple or blue colors.