Weather on Earth is highly influenced by events on our sun. Also the amount of solar spots and aurora borealis have a remarkable effect on radio wave propagation.
Geomagnetic, solar radiation storms and radio blackouts are caused by our sun. Particles emitted during solar flares, CME and X-Ray radiation have their effect on biological entities, power systems, spacecraft operations including GPS systems and on long range HF communications and LF navigation systems.
For more information visit the NOAA Space Weather site.
NOAA has developed a scale to quantify the effects of these solar activities. This scale has three parts: Geomagnetic Storms, Solar Radiation Storms and Radio Blackouts. Each of these indicators has a category range from 1 (minor) up to 5 (severe).
All categories are described showing there effect on power systems, spacecraft, satellites, biological life forms on Earth, HF radio and navigation.