What is a Plasma?

The Fourth State of Matter

Plasmas are often referred to as the fourth state of matter, but what does that really mean? You may be familiar with the more common 3 states of matter–solid, liquid, and gas–but what happens beyond gas? If we take the familiar example of ice, as it is heated it will turn into water, and then eventually steam. But if we continue to add heat to the steam, eventually the water molecules will begin to break apart into individual atoms of hydrogen and oxygen, and then as more heat is added into ions and electrons. It is this super-heated mixture of electrons and ions that we call “plasma”. This state of matter is ionized as at least one electron has been stripped from the nucleus. Matter is only considered to be a plasma when a certain amount of all the atoms are ionized.

Examples of Plasma in Everyday Life

Plasma is an exceptional thing but what you don’t know is that it’s all around us. The most recognizable plasma we interact with every day is the sun. The sun is a very high temperature and density plasma as are all other stars. This plasma is sometimes ejected in the form of solar flares. These solar flares and other high energy particles interact with our atmosphere to generate another form of plasma. This is the Aurora Borealis. Another example that may seem more tangible is lightning seen in a storm made from our atmosphere being ionized by the electricity moving through it. However, the plasma that is closest to home, maybe even in your home is the electricity flowing through a fluorescent light bulb. Additionally, the lightning seen in thunderstorms is another form of plasma. Lightning is caused by electricity traveling through the air and ionizing the areas it travels through, creating a great conductor path. Plasma is something that is only seen in conditions that are very extreme, yet the extreme conditions are still readily observable  by everyone.

Plasma Physics Basics

The high energy state of plasma and it’s other unique properties create challenges for being able to study it. Plasma Behaves much like a fluid, but it also has charges which can flow like an electrical circuit. That means that to be able to describe plasma we have to use equations for both fluids and Maxwell’s equations of electricity and magnetism. Due to the charges in plasma it can be affected by magnetic fields and this is one way that we use to contain them. We can also use electric measurements of current and voltage to measure plasma. These properties are used in confinement systems which then allow us to study plasma. We use a wide variety of tools to learn about the exciting and complicated topic of plasma.

Image Credit- NASA Solar Dynamics Observatory