Why a superconductor expel magnetic lines of force from inside completely when cooled below critical temperature?

Suppose a superconductor which is in a normal state (i.e. $T>Tc$) is subjected to a magnetic field. As soon as magnetic field switched from 0 to some value, eddy currents will develop on the surface and they will die away because of finite resistance. Now if I decrease the temperature below critical temperature, normal material will become superconductor and it will expel the magnetic field immediately, cf. the Meissner effect. I want to know the reason what causes the superconductor to push away magnetic fields.

• Have you read en.wikipedia.org/wiki/London_equations ? – PM 2Ring Sep 8 '18 at 9:54
• Yes I did. I have gone through London's original paper. However, I think it do not explain why magnetic filed push out from inside. It will you how magnetic filed will penetrate a superconductor and proves that magnetic filed could not live inside a superconductor mathematically. But why.. the physical reason remained un-explained. I would be happy if you explain it to me – Nilabja Kanti Sarkar Sep 8 '18 at 10:15