A Resonance is a type of weather phenomenon that only occurs during nighttime. It causes the skies above an area to be lit as if it was being lit up by artificial lighting, when it is actually not. Unfortunately when taken a photo of using a camera, it does not look natural and will look like as if light was coming from an artificial source. This phenomenon normally occurs in the skies above large cities within Arasia, most notably Aulump City.
There are no positive or negative effects caused by this weather phenomenon. The only visible difference is that when you are under the area where a resonance is present, areas that are normally dark at night will appear brighter than it normally is.
Some scientists believe that resonances occur due to light pollution, but this cannot be confirmed as the lighted nightsky of a resonance does not come from any artificial sources.