Why do we care about solar activity? Of course, solar activity is of interest to astronomers but it can also have major consequences on the Earth.
Credit: ESA and NASA/SOHO
For example, the ionosphere is a region of the atmosphere that becomes ionized by cosmic rays. So greater amounts of cosmic radiation can cause changes in that layer. This can block GPS signals as they try to penetrate the atmosphere. It can also cause interference in the high frequency radio waves that travel through the ionosphere. Also, the charged particles that comprise cosmic rays can cause problems in the electronics. Whenever charged particles are moving near a conductor they can cause additional currents in the conductor. These currents can be bad for electronics (like the instruments in satellites or the avionics in airplanes). This can even cause problems in the electrical infrastructure. The small currents caused in your cell phone by cosmic rays are unlikely to be damaging but if the currents are forced into something of the scale of a powerline it can be a problem, particularly because powerlines are set up for an AC current but cosmic rays would produce something more like a direct current. For example, in 1989 the entire Canadian province of Quebec was blacked out as a result of a solar storm (more on that here: http://www.nasa.gov/topics/earth/features/sun_darkness.html )
Cosmic rays can have big consequences on the Earth
Cosmic radiation can also possibly have health effects. Normally at ground level this is a very small risk because we are protected by the atmosphere. Even when traveling in an airplane it is probably not a big worry because there is still some shielding happening and the time spent in the air is small. But it is something aviation professionals should keep informed about. It is particularly important to study cosmic rays at the poles because the levels of cosmic radiation are higher near the Earth’s poles because particles can become trapped in the Earth’s magnetic field and follow the field to the poles. This is becoming an area of even greater interest because in recent years more and more flights are going over the North Pole and other arctic regions (more on that here: http://www.nasa.gov/centers/langley/science/polar-radiation.html ).
A Nowcast of Atmosphere Ionizing Radiation for Aviation Safety (NAIRAS) model. Credit: Science@NASA