What effect does lowering a signal’s transmitted elevation angle have on ionospheric HF skip propagation?

The elevation angle (or angle of radiation) is the angle at which a radio wave departs the transmitting antenna relative to the horizon. When you lower this angle, the radio wave strikes the ionosphere at a much shallower incidence. Because of this shallow geometry, the refracted wave returns to Earth much farther away from the transmitter. Lowering the elevation angle does not change intrinsic ionospheric properties like the Maximum Usable Frequency (MUF) or critical frequency; it strictly extends the physical geometry of the skip distance.