The circular movement and the Chakra are always signs of energy in action, generally
The Sudarshan Chakra symbolises the action of Sri Krishna's force. A revolving disc means a force in action on the nature.
The force which you felt must evidently have been rising of the Kundalini ascending to join the Force above and bring down the energy needed to ease the depression and then rising again to enforce the connection between the Above and the lower centres. The seeming expansion of the head is due to the joining of the mind with the consciousness of the Self or Divine above. That consciousness is wide and illimitable and, when one rises into it the individual consciousness also breaks its limits and feels wide and illimitable. At such times one often feels as if there were no head and no body but all were a wide self and its consciousness, or else the head or the body is only a circumstance in that.
The Force ( the force of the higher spiritual or divine consciousness, the Mother's Force ) comes in various forms, vibrations, currents, waves, a wide flow, a shower like rain etc. It passes to each centre in turn, the crown of the head, the forehead centre, throat, heart, navel centres down to the Muladhara and spreads too throughout the body. The rotatory movement is the movement of the Force when it is working and forming something in the being.
This now was witnessed in that son of Force,
In him that high transition laid its base.
Original and supernal Immanence
Of which all Nature's process is the art,
The cosmic Worker set his secret hand
To turn this frail mud-engine to heaven-use.