Stellar winds have been detected and studies in several regions of our galaxy through space telescopes. These winds have variety velocities and ion compositions. Solar wind probing are shown different type of plasma phenomena with strong impact on the planets of the solar system. Today Voyager space probes launched on 1970 are more than 10 light-hours away from Earth and it is still possible to measure its effects. In this work the structure and variability of the solar wind and it’s interaction with planetary magnetic fields will be shown. The main issue of this research is to show the importance of magnetosphere as an Earth life keeper. Solar activity effects on Earth environment and life system are also analysed.

Earth’s magnetic field is works like a magnetic dipole, whose poles oscillate through the. We believe that the origin of Earth’s magnetic field is the convection of molten iron and nickel in the outer planetary core, along with the Coriolis Effect. The region around the planet containing charged particles and gas controlled by its magnetic field is the magnetosphere. There are other planets in the Solar System that contain magnetic fields that cause a magnetosphere. During the solar activity the sun uses to eject charged particles in all directions, with speeds and compositions that vary according to the latitude where they were emitted. It’s the solar wind and it was first detected at 70’s by MARINER. The flux of particles consists mostly of high energy electrons and protons that escapes from sun’s gravity because of their high kinetic energy associated with the high temperature of the plasma “atmosphere” of the sun. When these plasma particles escape from the gravity, they have a tangential velocity because of the rotation of the sun, and this gives a spiral shape to the solar wind, with a density that decreases with the distance from the sun. These particles can arrive at Earth with very high speeds and their interaction with the magnetosphere deforms Earth’s magnetic field, compressing the field lines and forming a long tail of hundreds of thousands of kilometers in the dark side, while the illuminated side has just a few tens of thousands of kilometers.

The interaction between the solar wind and Earth’s magnetic field is responsible for the geomagnetic storms, what makes the ionosphere unstable. During a geomagnetic storm aurora becomes observable in the sky in the pole regions, and many other effects are detected. Many communication systems utilize the ionosphere to reflect radio signals over long distances, and the incidence of solar charged particles can cause interferences in these electromagnetic waves, affecting TV and radio transmissions. GPS and others navigation systems are also affected by storms because of the variations in the density of the ionosphere they cause. This variation is also responsible for slowing and changing orbits of satellites and unless Low Earth Orbit satellites are routinely boosted to higher orbits, they slowly fall, and eventually burn up in Earth's atmosphere. Besides these technology injuries, solar radiation can be seriously harmful to human, nature and climate. Earth’s atmosphere and magnetosphere work as a shield that stops the high energy particles released by the solar flares. The human expose to these particles can cause cancer, chromosome damage and much others health problems, that astronauts in space are subjected to. Large doses of radiation can be fatal immediately. Some migratory animals like whales, birds and pigeons have a biological compass and are able to fell the magnetic field of the planet, and we know that magnetic storms have been responsible for pigeons race smashes.

The secret of life maintenance can be in the planetary magnetic field. So, besides the existence of water and the temperature, the detection of magnetic field can be the key of finding planets that hold life.