Arc Plasma Conductivity
The electrical conductivity of the ionised gas in the arc, which depends on electron density and gas temperature. It determines the electrical resistance of the path between electrode and workpiece.
The arc is a hot gas that conducts electricity. How well it conducts depends on the temperature and the amount of charged particles in it. The hotter the plasma, the better it conducts. This conductivity determines the voltage across the arc and thus how much heat goes into the weld. If the plasma is too conductive, the voltage collapses and the arc becomes soft and unstable. You can see that in a bad weld and lots of spatter. In practice, this means: keep the electrode clean and watch the gas flow. If the arc is erratic, it's often due to contamination or wrong gas. Then it helps to clean the nozzle and check the gas amount.