This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
SporadicENPS. Ray diagram of sporadic event HF radio transmissions above the normal layer MUF red pass through the layer During sporadic event signals blue will either be refracted or partially refracted in the layer resulting in decreased long distance transmission but better reception within the normal first skip zone Strahlendiagramm