Heliosphere

The heliosphere is the immense magnetic bubble containing our solar system, solar wind, and the entire solar magnetic field. It extends well beyond the orbit of Pluto. While the density of particles in the heliosphere is very low (it's a much better vacuum than is created in a laboratory), it is full of particles of interest to heliospheric scientists. Check out the image below for a diagram of the heliosphere.

Dynamics
The sun sends out a constant flow of charged particles called the solar wind, which ultimately travels past all the planets to some three times the distance to Pluto before being impeded by the interstellar medium. This forms a giant bubble around the sun and its planets, known as the heliosphere.

Protection
The heliosphere acts as a giant shield, protecting the planets from galactic cosmic radiation. Earth is additionally shielded by its own magnetic field, the magnetosphere, which protects the Earth not only from solar and cosmic particle radiation but also from erosion of the atmosphere by solar wind. Planets without a shielding magnetic field, such as Mars and Venus, are exposed to such processes and have developed differently.