What is Plasma?
is the fourth state of matter. Although the definition of plasma is
often simplified to being an "ionized gas," the true definition of
plasma is more complex than this, for some ionization is common in almost
every gas. Plasma can be defined more accurately and scientifically as
"a quasineutral gas of charged and neutral
particles which exhibits collective behavior" (Chen, 3). In
simplified terms, plasma is a gas that can conduct electricity.
is the most common state of matter; it is believed to comprise more than 99%
of our visible universe. Every time we witness a bolt of lightning or
gaze in awe at (or see photographs of) the Aurora Borealis, we are observing
plasma on Earth. The truth, however, is that we seem to live in the 1%
of our universe where naturally occurring plasma is quite rare.
Lightning and the Aurora Borealis are just two of the very few examples of
naturally occurring plasma on this planet. Plasma is relatively rare on
Earth because very high temperatures are often necessary for plasma
formation. In fact, at extremely high temperatures, all matter is in
the plasma state. This is true because heat causes atoms of a neutral
gas to speed up, thus increasing the probability and occurrences of
collisions; when atoms collide, electrons can be liberated from their parent
atom. The result is the creation of a charged gas (plasma). This
condition for plasma formation explains why plasmas are commonly found in
astronomical bodies with temperatures of millions of degrees, as well as why
they are rare on Earth.
Very high temperature is not the only condition that is conducive to plasma
formation. Gas also ionizes when it is rarefied; when a gas is
rarefied, freed electrons virtually never encounter an ion with which it can
rejoin. Plasma can also be formed when an exterior source of energy,
like an electromagnetic field, is so strong that it tears electrons free from
originally neutral atoms. The conversion of a neutral gas into a plasma
can occur extremely quickly. (The Pervasive Plasma State).
Why Study Plasma?
There are numerous everyday uses for
plasmas. For example, fluorescent lights and neon signs work because of
plasma. Circuit features on microprocessor chips in computers also
contain plasma. Even the exhaust that is emitted during rocket launches
is actually plasma, not gas. Plasma is also used to manufacture
industrial diamonds and superconducting films.
It may be the solution to our energy
problems. While the Earth's natural supplies of coal, oil, and natural gas
are being depleted, and the burning of fossil fuels creates harmful
pollution, fusion is raising the hopes of many scientists. After all,
the deuterium in the Earth's oceans is sufficient, through fusion, to
energize the world for millions of years at little or no cost to our
environment. And plasma is key in
fusion. This is true because fusion occurs when the atomic nuclei of
light elements are combined to create heavier nuclei. This nuclear
reaction results in the release of enormous quantities of energy. But
for fusion to occur, three conditions must be met. The particles must
be hot enough, in sufficient number (density), and well contained
(confinement time). All three of these conditions are observed when
matter is in the plasma state. Research in plasma physics could help
make fusion reactors part of our future.
Studying plasma will hopefully unlock the
secrets of space weather and allow scientists to forecast space weather more
accurately. Since stars, nebula, and other galaxies are primarily
plasma, studying plasma will hopefully answer many of the lurking questions
about such topics as how stars are created and how they die.