I was reading an article about magnetospheres, and came across this quote:
This supersonic ionized gas, or plasma, called the solar wind carries with it a magnetic field and a frame dependent electric field. The frame-dependence arises due to the high electrical conductivity of the plasma and its magnetic field.
What does 'frame dependent electric field' mean? Does one often talk of frame dependence in relation to electromagnetism, or it this term used generally in context of astronomy?