Which ionospheric region is closest to the surface of Earth?
The D region✓الإجابة الصحيحة
The E region
The F1 region
The F2 region
الشرح
The ionospheric D layer is the lowest, extending roughly from 60 to 90 km above Earth, beneath E at about 100 to 125 km and the still higher F1 and F2 layers. An upward-traveling radio wave therefore encounters this layer first.