A symposium was held at the Union Radio Scientifique Internationale (URSI) General Assembly in Kyoto in 1993 to review research concerning electric fields that have a component parallel to magnetic field lines; that is, when E.B is not equal to zero. Under these conditions the frozen-in-theorem of ideal magnetohydrodynamics is not applicable. Indeed, E.B = 0 is one of the cornerstone conditions on which the demonstration of this well-known theorem is founded.
The similarity between laboratory double layers and those observed in the magnetosphere is not always obvious. However, the symposium, Parallel Electric Fields in Laboratory and Space Plasmas, showed that cross fertilization of laboratory plasma physics and space plasma physics can be achieved.