How can a geomagnetic storm affect HF propagation?
Improve high-latitude HF propagation
Degrade ground wave propagation
Improve ground wave propagation
Degrade high-latitude HF propagation✓Правильный ответ
Объяснение
During a geomagnetic storm energetic particles are funnelled along field lines into the auroral zones, raising D region absorption there while the disturbed F region loses ionisation, so paths crossing high latitudes degrade first and worst. Ground wave travels along the surface and does not involve the ionosphere, which rules out the ground wave choices.