The higher the Aurora Level, the more Aurora activity, hence the more high-latitude absorption of your radio signal. The higher the K index, the worse conditions are now. And the forecast tells you the trend. The lower the Aurora Level, the better for HF communications over the poles and high latitudes. Noise can get very high, especially here in the Pacific North West.
Signals get weaker than normal on some bands, and deep fades occur.
This bubble is ejected from the Sun. This ejection of gas lasts for several hours, and if it is directed toward the earth, can result in a very high energy bombardment into our atmosphere and ionosphere. And our Geomagnetic field becomes very active. A highly active Geomagnetic field degrades radio communications. See more here .