Ideal voltage source connected with ideal Inductor
The situation will look like this: 



From t = 0s to t = 2s we have a "charging phase" and the flux will "follow the current". Thus the magnetic field will rise.  

But from t = 2s to t = 4s the current will start to decrease and we have a "discharge phase" and magnetic field collapse too (flux follow the current).  

But at time t= 4s all the energy stored in the inductor was released (I = 0A and Flux = 0Wb). But due to the input voltage is still present across the inductor. The inductor will start a charging phase and it will start to store the energy in the form of a magnetic field.