As I mentioned couple of days ago I will be going trough my plasma books and witting about things I go over.  So start of the first post I guess I should give a brief introduction to plasmas.

Currently there are four know states of mater, plasma is one of them.  Most people are familiar with solid, liquid and gaseous states of mater, but very few people know much about plasma.  It is said that about 99% of all matter in universe is in plasma state, yet on Earth we see very little plasma.  This is because the thing that makes mater transition from one state to next is temperature.  In the case of water ice is the solid state and it occurs when temperature is below 0C, liquid water occurs between 0-100C and above 100C is vapor or water’s gas state.  In order to make water into plasma we would have to raise the temperature of the water to thousands of degrees, which is very impractical here on Earth, but on Sun and billions of other stars it’s a completely different story.

What makes plasma unique is that, while for all other states of matter molecules and atoms stay intact, in plasmas the dissociate from each other.  This means that the ions get created.  So if you have some hydrogen atoms floating around when the temperature gets increased they will start to move extremely fast, so fast that when they hit into each other they would loose an electron.  This electron would flow freely in space until is captured by another free proton that’s floating in space.  In plasma this happens constantly and in the end we have a very large number of free protons and electrons zooming around, but we have very little of actual Hydrogen left.  Free protons are also known as ions.  In the case of other elements like Helium the ion would be two protons and 2 neutrons which were part of the nucleus.  In the case of Helium all or some of the electrons could be knocked out, all depending on the temperature.

In general in places, such as stars, where temperatures reach millions of degrees, plasma is fully ionized.  This means that all of the original elements have been broken up into free electrons and ions.  This is not the case for most situations.  In order to figure out how much ionization we have we can use the Saha equation.

(Eq. 1: Saha equation)

In Saha equation we can see that the ratio of (number of ionized electrons) and (number of “neutral”, or un-ionized atoms) depends on the temperature and (ionization energy of the gas).  Here K is the Boltzmann’s constant and T is temperature in Kelvin.

So for now this should be it.  In next installment I will try and describe Debye shielding and plasma parameters necessary for plasma to happen.