Problem 3 – Hint 2

Fluid particles can move freely along the magnetic field lines, but not across them: the magnetic flux through material loops is constant, due to the infinite conductivity of the fluid combined with Faraday’s law. A material loop is a fictitious loop, each point of which has the same velocity as the fluid molecules in its immediate vicinity.

Please submit the solution to this problem via e-mail to The next hint for the Problem 3 will be published at 13:00 GMT, 19th February 2023, together with the next updates of the intermediate results.