How does the potential get from A to B in a plasma?

Summary form only given. It is noted that the question, how does the potential get from A to B in a plasma, has important consequences for basic plasmas, plasmas in the Earth´s magnetosphere, plasmas in tandem mirrors and in tokamaks, and plasmas used in plasma processing. In solving the problem, nature may have created auroras. The answer often depends on whether the reference frame is moving or stationary and on the dimensionality of the problem. Until recently, the answer made it impossible to carry out many RF experiments in tokamaks but provided a key ingredient to semiconductor etching and some axial plugging in tandem mirrors.