Hi Magnetic pressure and tension are somewhat established concepts. They can be imagined as a lot of small magnets, like bar magnets, lined up in the same direction and equally spaced parallel and perpendicular to their direction, like this
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Pressure is in this case a repelling vertical force perpendicular to the magnetic to the bars and the magnetic field lines. This is because the same poles of the bar magnets come closer to each other when pressure is increased and vertical distance shortened. Tension is an attractive force in this case horizontal between the magnets. This is because opposite poles of the small bars magnets are close to each other in the horizontal direction. My questions are the following. Imagine a small disturbance in the vertical position of a small bar magnet, with what speed will this motion propagate? Since this is equal to a change in the magnetic pressure we can call it the magnetic pressure sound speed. Imagine a small disturbance in the horizontal position of a small bar magnet, with what speed will this motion propagate? Since this is equal to a change in the magnetic tension we can call it the magnetic tension sound speed. In the case of bar magnets the mass of the magnet will determine the magnetic sound speeds but how will the case be in the more continuous case of a plasma? Will the magnetic field lines stay in specific plasma particles so that the density of the plasma will determine the speeds or are the magnetic field lines connected to some other structure in the plasma? I need to know this because I intend to determine at what speed shock waves can be expected in certain plasmas. Magnetic shock waves will develop when the speed of the plasma exceeds the magnetic pressure and tension sound speeds. Combined with the traditional kinetic gas sound speed there could be different shock waves since the kinetic gas sound speed doesn't have to be identical to the magnetic sound speeds. I have heard of such experiments with two shock waves in ionized gases. If someone knows about such experiments please send me references. David
