Although people do not think about it often, the magnetosphere of the Earth is vital to life on earth because it helps to protect the surface of the earth from the solar wind of the sun. There is even significant question as to whether life could exist on the planet if the magnetosphere did not exist. This begins with the understanding that there is a lot of radiation in space, but it is not limited to that.
The magnetosphere is at its most basic a magnetic field that surrounds the earth. This field extends about 36,000 miles into space with the north and south poles being the poles of the magnetic field¹. In fact the earth has the strongest magnetosphere of any of the rocky planets. This means that a majority of the particles which are carried on the solar wind are prevented from reaching the earth’s surface. This is able to dramatically reduce the effect of solar winds on the planet earth, but there are still effects.
One of the easiest of the effects of the solar winds to see is in the far north or far south is the aurora borealis. These are lights which can be seen on dark, clear nights which are made by protons and electrons interacting with the magnetic field of the earth. These do not generally have all that much effect on anyone, but it is a good example of how the two interact.
Since solar winds can vary dramatically based on things like solar flares this can lead to solar storms². For most of human history these storms were largely unknown. On earth these can increase radiation, but overall they do not create enough on earth to be a problem. The real issue is that of outer space. Satellites are one of the most common things in space and unprotected they could be damaged by solar storms and are occasionally interrupted by them³. This same radiation and which can damage a satellite is far more dangerous to anyone who is in space. For short trips the radiation is minor, but plans for long space trips such as those to mars have to focus on limiting radiation for astronauts with lead shielded areas though there are some discussions of creating a magnetic field around the ship to help reduce overall radiation.
By limiting the amount of solar wind which reaches the earth is vital to the health and wellness not only of humans and animals, but for technology as well and as we travel out into the solar system understanding this magnetic shell protects earth is going to become one of the factors in being able to travel to other worlds as well as helping to understand the Earth better.
1- http://www.windows2universe.org/earth/Magnetosphere/aurora.html
2- http://solarscience.msfc.nasa.gov/SolarWind.shtml
3- http://image.gsfc.nasa.gov/poetry/workbook/storms.html
