Page 38 - Curriculum Visions Dynamic Book

Solar wind
The flow of charged particles (which together are described as plasma) occurs outward in all directions from the Sun, and it creates the solar wind. The solar wind reaches to the outer regions of the Solar System, perhaps traveling beyond Neptune.
Particles move outward very quickly within the corona. They start at a speed of up to 700 km per second, then slow down gradually toward the outer edge of the Solar System. In the region of the Earth their speed is about 400 km per second—about the distance from New York to Washington, D.C.
The particles in the solar wind have a considerable effect on the Earth because they interact with the Earth’s magnetosphere. They cause a wide range of phenomena, including radio interference and the auroras (see page 45).
The solar wind also blows the tails of comets away from the Sun and even has measurable effects on the path of spacecraft. As a result, it has been suggested that by building a sufficiently large solar sail, it would be possible to be carried through the Solar System on the solar wind.
comet A small object, often described as being like a dirty snowball, that appears to be very bright in the night sky and has a long tail when it approaches the Sun.
magnetosphere A region in the upper atmosphere, or around a planet, where magnetic phenomena such as auroras are found.
neptune The eighth planet from the Sun in our Solar System and five planets farther away from the Sun than the Earth.
plasma A collection of charged particles that behaves something like a gas. It can conduct an electric charge and be affected by magnetic fields.
radio interference Reduction in the radio communication effectiveness of the ionosphere caused by sunspots and other increases in the solar wind.
solar wind The flow of tiny charged particles (called plasma) outward from the Sun.
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Solar sail
If you have ever watched a radiometer (a glass bulb with little black and silver panels inside that spin when the Sun shines), you will already be familiar with the idea that the Sun can, in one way or another, send energy across space.
A solar sail works because the Sun sends out particles that form the solar wind. A solar sail catches sunlight. As Newton’s laws of motion tell us: For every action there is an equal and opposite reaction. When photons in the solar wind hit a solar sail, they apply a force to it. The sail applies an equal and opposite force that moves it away from the Sun.
There is no end to the solar wind, and so there is a slight but constant force applied to the sail. The result is that it is constantly accelerating. In time sunlight could move a sail faster than any rocket could power a spacecraft.
Such a solar sail would have to have a large area and be made of the lightest material. The low mass is important because acceleration is force divided by mass. The bigger the mass, the smaller the acceleration.
Suitable solar sail material would be metal-coated plastic. Sails could be large disks, or they could have large blades.