Plasma (physics)

Plasma is the 4th state of matter.

A plasma lamp, showing some of the more complex things a plasma can do. The colors come from the gas in the lamp. Each type of gas makes a different color

Gas-filled tubes often contain plasma. This one shows neon. The color of the tube gives a hint to the gas inside

Plasma is created by adding energy to a gas so that some of its electrons leave their atoms. This is ionization. It results in negatively charged electrons, and positively charged ions. Unlike the other states of matter, the charged particles in a plasma react strongly to electric and magnetic fields (i.e. electromagnetic fields). If a plasma loses heat, the ions will re-form into a gas, emitting the energy which had caused them to ionize.

Over 99% of the matter in the visible universe is believed to be plasma. When the atoms in a gas are broken up, the pieces are called electrons and ions. Because they have an electric charge, they are pulled together or pushed apart by electric fields and magnetic fields. This makes a plasma act differently from a gas. For example, magnetic fields can be used to hold a plasma, but not to hold a gas. Plasma is a better conductor of electricity than copper.

Plasma is usually very hot, because it takes very high temperatures to break the bonds between electrons and the nuclei of the atoms. Sometimes plasmas can have very high pressure, as in stars. Stars (including the Sun) are mostly made of plasma. Plasmas can also have very low pressure, as in outer space.

On Earth, lightning makes plasma. Artificial (man-made) uses of plasma include fluorescent light bulbs, neon signs, and plasma displays used for television or computer screens. Plasma lamps and globes which are popular children's toys and room decorations.

Scientists are experimenting with plasma to make a new kind of nuclear power, called fusion, which would be much better and safer than ordinary nuclear power, and would produce much less radioactive waste.

Plasma (physics) Media

Plasma microfields calculated by an N-body simulation. Note the fast moving electrons and slow ions, resembling a bodily fluid.
Artist's rendition of the Earth's plasma fountain, showing oxygen, helium, and hydrogen ions that gush into space from regions near the Earth's poles. The faint yellow area shown above the north pole represents gas lost from Earth into space; the green area is the aurora borealis, where plasma energy pours back into the atmosphere.
Lightning as an example of plasma present at Earth's surface:*Typically, lightning discharges 30 kiloamperes at up to 100 megavolts, and emits radio waves, light, X- and even gamma rays. Plasma temperatures can approach 30000 K and electron densities may exceed 1024 m−3.
The complex self-constricting magnetic field lines and current paths in a field-aligned Birkeland current that can develop in a plasma.
Simple representation of a discharge tube - plasma
Artificial plasma produced in air by a Jacob's Ladder
Avalanche effect between two electrodes. The original ionization event liberates one electron, and each subsequent collision liberates a further electron, so two electrons emerge from each collision: the ionizing electron and the liberated electron.
Image of a Hall thruster in operation. I took this photo and claim no copyright.
This movie exhibits a number of interesting solar phenomena. The primary feature of interest is the whirrling tower of plasma on the lower right limb.