Ground wave propagation--- wave propagation is any of the ways in which waves travel. Its a method of radio wave propagation that uses the area between the surface of the earth and the ionosphere for transmission.

Its perpendicular to the direction.

It oscillates for transverse waves.

Sky wave propagation---- it i a type of radio wave propagation it is either the reflected or refracted back waves to the earth from the ionosphere which is an electrically charged  layer of the upper atmosphere.

Sky wave is better at night as it turns out the ionosphere reflects certain frequencies of the radio waves.

Space wave propagation---- this is defined a  radio wave propagation that occurs within the 20km of the atmosphere like troposphere comprising of a direct and reflected waves.