You are fully in touch with your authentic self doing something you love, and as a result are completely in that Now moment where everything flows. Your attention is fully absorbed in what you're doing and outside distractions just don't exist.

It sounds like a similar sensation to an experience I often get. Commonly whilst getting involved in something you find relaxing or enjoyable to your personal preference. One seems to 'switch off' and 'flow' as you say, through the activity.

It's as if you are pleasing the soul and sticking to it's intent- thus becoming absorbed and allowing the constant mind narration to halt for a while.

This experience is wonderful and quite therapeutic, it's as if you are bursting with an unexpected energy and you can completely enjoy the moment.

I would call it a moment of Alignment.

I experience this while sparring against my whole Karate class, when you are in the flow you are calm relaxed and in the moment. While everyone is around me trying their best to punch kick or strike me I am in a pure what next state of mind, a state of survival and what do I need to do next where do I have to go. What is fun is the fact that everyone thinks separately so it is total chaos and this makes it easier for me. If somehow everyone were to cooperate to get me then I'd be in trouble, but no everyone wants to get me so I can get them in each other's way and be the artist of confusion but for me I am the artist in perfect control.

According to this site you are in the Vortex. Search for it on the site.

Nevertheless, I think of it as enjoying ones self and being.