How to Make a SQUARE Vortex Ring! ft. 3blue1brown

I thought a different reason for this , correct me if I am wrong.
When a circular vortex passes through a square ring ,at that point particles colliding with ring neutralizes resulting in division of ring in four parts .
Suddenly at that moment the particles at terminal of ring parts start attracting their consecutive ends through gravitational pull ,hence resulting in distortion of circular shape. 
 Story does not end here after that when both the ends( of different parts) collide they have some momentum at that point hence resulting in same type of motion in opposite direction. Hence giving a shm type motion in shape of resulting vortex .