In german physics introductory texts often the following experiment is cited which "shows" that a changing magnetic field can induce an electric field with has closed field lines. Here is a picture of the setup: 

![](https://i.stack.imgur.com/iUV4v.jpg)

A high frequency ac-voltage is applied to a coil around a glass sphere which is filled with a gas. Then a circular lighting effekt occurs as shown on the image. 

I have some questions about this:

1. How is this experiment called in english? Do you have references of textbooks or papers which discuss this in detail?
2. Why is it reasonable to say that this experiment "shows" that there "must" be a circular electric field? Let general epistomology aside, I think that the rough theory about this is, that the electrons wiggles back and forth because of the changing induced electric field. Since the magnetic field changes in sign the mean lorentz force due to the magnetic field is zero, so the lorentz force doesn't matter here. But if you don't know that the field lines are circular, especially that the field vectors are tangential to the circle, how conculde this from the experiment? For example it could be conceivable, that the field changes from radially invards to radially outwards and we get a radial wiggling of the charges which produce the lighting!? 
What (and what not) can one reasonable "conclude" from this experiment about the nature of the induced electric field and why?
3. How can one describe this experiment mathematically in detail?
4. Are there other, perhaps better or clearer experiments which demonstrate the existance of closed electric field lines produced by induction?