Tom Smith examines the plasma globe to the left.;  Darkness allows the brilliance of the plasma streamers to be appreciated.

The Plasma Globe setting on a pedestal showed bright blue plasma streamers over a dark background. Trekkies may recognize the plasma globe from when it appears behind the heads of the "Borgs" in Star Trek. After admiring the bright streamers, the next logical thought for most engineers would be, "How does it work?" Further research yielded an explanation.

Inside the plasma globe, electrons are traveling from the electrode to the outer surface and there is also an oscillating electromagnetic field present. This electron motion is required to generate the plasma. Plasma is defined as an electrically neutral gas that is intensely ionized with charged particles such as electrons and ions. When electrons separate from a parent atom or molecule, that atom or molecule becomes an ion. The negatively charged electron and the positively charged ion move about within the plasma, thus changing the local characteristics of the electromagnetic field. This change along with the oscillating electromagnetic field from the electrode will excite ions, molecules, and atoms. Upon becoming excited, these particles (charged or uncharged) will swiftly radiate photon (light) energy. The photon energy is what makes plasma so visible. The overall appearance of the plasma globe is determined by the characteristics of how the electromagnetic fields combine.

While observing the plasma globe demonstration, one might wonder what determines the appearance of the bright blue streamers. It is actually the pressure in the globe that decides the characteristics of the streamers. The distinction should be made that the pressure inside of a science demonstration plasma globe is significantly higher than the pressure in most plasma chambers used by scientists for experiments. It is essential that pressure within a plasma globe be quite high in order to see the streamers. Due to the tremendously high pressure, the plasma gets hot when it is generated. Based on the principles that hot air rises, the hot plasma streamers tend to move up the side of the globe. The hot region of plasma is highly conductive, and so the streamers remain intact until broken by instability.

The pressure in the globe is very important for the success of the plasma globe display. If the globe pressure is too high, the potential of the electrode will not be sufficient for the electrons to generate plasma and there will be no streamer. The result would be a dark globe with no light. Conversely, if the globe pressure is too low, the "fluid" effects of the streamers will be absent. The globe would be illuminated overall with a low intensity light, but it would not have any streamers.