With an increase in solar activity comes an increase in solar flares. Astronauts are at much greater risk than crew of commercial aircraft. However some aircraft are exposed to increased levels of radiation during solar storms. Earth's atmosphere and magnetosphere allow adequate protection for us on the ground, but astronauts in space are subject to potentially lethal dosages of radiation. The penetration of high-energy particles into living cells, measured as radiation dose, leads to chromosome damage and, potentially, cancer.
Large doses can be fatal immediately.
In October 1989, the Sun produced enough energetic particles that an astronaut on the Moon, wearing only a space suit and caught out in the brunt of the storm, would probably have died. Solar proton events can also produce elevated radiation aboard supersonic aircraft fly ing at high altitudes over the polar caps. To minimize this risk, routine forecasts and alerts are sent through the FAA so that a flight in potential danger can alter its course and reduce altitude to minimize radiation exposure. During the solar maximum, the intensity of the solar wind increases deflecting some galactic radiation away from the solar system. This means that while the Earth may experience an increase in solar radiation over this period, the amounts of galactic radiation may drop.