Tesla Bifilar coil Magnetic Field shape

[indio007]

Anyone have an image if the magnetic field shape of Tesla's Bifilar coil?

[evostars]

Its an old post, but an important question none the less. So here's what i know.

I once saw this image.
The current flows in spairals inwards, so the magnetic field flows over the coils (at 90 degrees to the current flow) from outside to the inside. The other direction on the other side.

This drawing shows straight lines. but the current spirals, so the field also spirals in and out.