Although the magnetic field at this distance is weak, it is still capable of holding within it masses of highly energetic plasma. As the solar wind approaches the Earth's magnetic field, a highly supersonic shock wave is created sunward of the Earth somewhat analogous to the shock wave created when a jet plane breaks the sound barrier. This shock wave is called the bow shock. Most of the solar wind particles are heated and slowed at the bow shock and detour around the Earth through a volume of space called the magnetosheath. Some particles are actually reflected back from the bow shock into the solar wind stream in a region of turbulence called the foreshock.
Some particles rush through funnel-like openings at the poles, called the polar cusps.
Many of these energetic particles descend Earth's magnetic field lines to enter the upper atmosphere and create the aurorae-the visible signature of the otherwise unseen energy transfer from the Sun to the Earth. Events on the Sun can also trigger other changes in the electrical and chemical properties of the atmosphere, in the region above the atmosphere known as the ionosphere, and out into the magnetosphere. These changes cause magnetic storms, communications static, power blackouts, and navigation problems for ships and airplanes with magnetic compasses. Also, satellites and spacecraft can be damaged or can re-enter the atmosphere prematurely because solar storms increase the density of the atmosphere, and hence the drag on satellites. The ability to anticipate particle outbursts and fluctuations in the plasma flowing from the Sun and in the magnetic field due to solar activity will be increasingly useful as more of our science, commerce depend on the operation of vehicles in space.