Effects on HF communications and Navigation
HF communication depends on the reflection of signals through the ionosphere. During a major solar flare an increased ionisation in the ionosphere cause radio wave signals to be affected. The disturbance in the ionosphere can be due to solar flares, solar energetic particles (in the high latitude regions) or coronal mass ejections (CMEs). Disturbances in the ionosphere can also cause degradation in GPS range measurements and in severe circumstances, loss of lock by the receiver on the GPS signal.