Propagation away from the great circle bearing between stations
Successive ionospheric refractions without an intermediate reflection from the ground✓Правильный ответ
Propagation across the geomagnetic equator
Signals reflected back toward the transmitting station
Объяснение
Chordal hop means the wave is refracted by the ionosphere, travels a chord to another point in the ionosphere, and is refracted again, never reaching the ground in between. Departing from the great-circle bearing, crossing the geomagnetic equator, and returning toward the transmitter each describe a different propagation effect.