Answer: dayglows

AnswerCrossword Clue
dayglowsDAYGLOW, airglow seen during the day
dayglowsairglow seen during the day
dayglowsdim light from the upper atmosphere caused by emissions from atoms and molecules ionized by solar radiation: observed at night (nightglow), during the day (dayglow), and at twilight (twilight glow), with each having slightly different characteristics