A vortex ring is a circular shaped ring of spinning gasses that move together as a unit. A vortex ring can happen in liquid or gasses, but are rarely seen because they happen inside of liquids or gases. When a vortex ring happens inside of suspended particles—as in the smoke rings which are often produced by smoke they can be seen. Visible vortex rings can also be formed by the firing of certain artillery, in mushroom clouds, and in microbursts.[1][2]
A vortex ring usually tends to move in a direction that is perpendicular to the plane of the ring and such that the inner edge of the ring moves faster forward than the outer edge. Within a stationary body of fluid, a vortex ring can travel for relatively long distance, carrying the spinning fluid with it.