Three times a day, every day—roughly 9am, 2pm, and 8pm Coordinated Universal Time—an extremely low frequency electromagnetic pulse races around the Earth, reverberating between the lower edge of the ionosphere and the planetary surface. These pulses correspond to the peaks of daily lightning activity along the world’s three “lightning corridors” in Africa, South America, and Southeast Asia.

Norsk tid: kl.1100, kl1600 og kl2200.
https://www.damninteresting.com/nugget/schumann-resonances/