Friend: One way of describing a a scalar wave is as a synthesis of transverse waves. It is typically a standing wave (in our 3 dimensions) while having amplitude in the time dimension. I do not agree with your other characterizations because they are imprecise and vague. Moreover everybody says "Tesla coils" as if they know what they are talking about. Tesla had a lot of inventions and it just seems juvenile to lump all of Tesla's work into a heap and call it a "Tesla coil". Now you may indeed know what you're talking about but the use of precise language would help anons determine if you are just spouting garbage or if you have a bit of knowledge/experience in the area. EVERY Every wave expands forever and ever; that is not a property unique to a scalar (longitudinal) wave. You have combined some ideas in the same sentence that don't belong together. When you say "contracts back every time" you are speaking about something different, a phase-conjugate mirror, a nonlinear optics phenomenon that pertains to normal electromagnetics and normal transverse waves but can be involved in converting normal EM into scalar EM. Get your terminology straight, study some physics, and then maybe anons will give ear to your discourse.