The magnetic current acts as the primary receptive force, splits into both water and air energy, is called yin in Chinese Taoist theory, exists at all three levels of existence (material, astral and mental) and is primarily trained via the fasciae tissue in the body.
The magnetic current flows via the fasciae tissue network and is cold and contracting, sometimes manifesting as an downward/inward pushing sensation. This is most often trained through expanding the ligaments/tendons in the body via pulling them open.
Sit in a chair or stand up with your feet shoulder width apart. Now hold your arms at shoulder level and pull your joints open as if someone were grasping your hand by the wrist and trying to pull you forward. Feel your joints open and hold it there while breathing freely.
At some point your will begin to feel a pulling type of force leading from your fingertips down into your core or potentially the floor.
This is the magnetic current or what they Chinese refer to as true yin. Prior to studying with my current teacher I had never encountered this method. Students on mine with years of tendon training experience have found revisiting their training with this method has led to rapid advancement in their various skills.
Learning to generate the force upon command and then shutting it off is the first step. After that most of your effort is centered around reinforcing the effect.
Magnetic energy splits into the water and air energies at the elemental level and has an indirect relationship to lunar energy as well. On a mental level it works with the emotion and feelings, on the astral level is impacts the receptive emotions and on the physical level reinforces the ligaments and tendons as well as allows you to throw people using fah jing. Extensive practice with this will allow you to develop what Charles Atlas referred to as a magnetic personality.
Generally speaking, train electric and magnetic energy in equal amounts. Long term focus on either energy in isolation results in some interesting psychological deviations that can be difficult to correct later on and if taken to an extreme can cause some health problems as well.