What term describes an area that is too distant for reception of ground waves, but too close for reception of ionospheric waves?

The 'skip zone' (sometimes called the dead zone) is a ring-shaped area around a transmitting antenna where a radio signal cannot be heard. This occurs when the location is beyond the reach of the transmitter's ground wave but not far enough away for the skywave to bounce back to Earth. Ground waves travel along the Earth's surface but eventually attenuate and fade out. Meanwhile, skywaves travel upward and are refracted back down by the ionosphere, landing at a significant distance away. The gap in coverage between where the ground wave dies and the skywave lands is the skip zone. The other terms do not accurately describe this specific phenomenon. A 'shadow zone' typically refers to an area where a signal is blocked by a physical obstruction like a mountain, not by propagation geometry.