Q: Are the northern lights present in...

Q: Are the northern lights present in the daytime, even though they cannot be seen?

A: The lights, formally known as the aurora borealis, are caused by an electrical disturbance in the atmosphere produced when high-speed particles from the sun interact with the Earth’s magnetic field, and researchers had long assumed that they were present in the daytime as well as at night. New research from the Johns Hopkins University Applied Physics Laboratory, however, indicates that this is not the case.

Using 10 years of satellite measurements of electrical disturbances, the laboratory team reported this summer that the northern lights are present predominantly in darkness, most often between sunset and midnight and mainly during the spring, winter and fall months of short days and long nights. During the daytime, the electrical conductivity of the atmosphere is too high for the lights to be created.