Re: How can you predict plasma temperatures?

Dear Isaac:
Most plasmas can be made only by pumping energy into the plasma.  The only 
plasmas that generate their own heat from reactions in the plasma are the 
sun and other stars, who's reactions are similar to those in a hydrogen 
bomb or in a fusion reactor.  A nuclear fusion reactor, if they ever get 
one built, will generate its own heat from reaction and create net energy.

Remember that a plasma is made up of positive and negative particles.  
These attract each other and so if left by itself the plasma will go out 
because the charge will neutralize itself and there will be no ions left.  
The only way to keep the plasma going is to pump energy into it to keep 
making ions as fast as they disappear.   The fusion reactor gets around 
this because it operates at very high temperatures and nuclear reaction 
take place which generate heat at those high temperatures.

The plasma temperature, however, can be very high.  A plasma torch 
operating in the air can reach several thousand degrees temperature but 
only because you are pumping electrical energy into it to keep it going.  
In that sense the temperature in the plasma can be calculated and 
predicted-but remember you must coutinuously pump energy into the plasma 
to make it start and keep going.

R. Bersin.....