F2 layer

The highest constantly observable ionosphere layer, characterized by a distinct maximum of free-electron density at a virtual height from about 135 miles (225 kilometers) in the polar winter to more than 240 miles (400 kilometers) in daytime near the magnetic equator. Also known as Appleton layer.

Related terms:

• F1 layer
• E layer
• D layer
• layer
• F layer
• boundary layer
• active layer
• surface boundary layer
• upper mixing layer
• layer depth effect