(Solved): The Grad-Shafranov equation is probably the most well-known MHD equation in the field of fusion pla ...

The Grad-Shafranov equation is probably the most well-known MHD equation in the field of fusion plasmas. In practice the nature of solution depends on the choice of two functions $I_0\left({?}_0\right)$ and $P_0\left({?}_0\right)$ and of boundary conditions. Now, consider "SOLOVIEV EQUILIBRIUM " with, ${?}_0(r,z)=A{z}^2\left(r^2+B{R}_m^2\right)+C{\left(r^2?R_m^2\right)}^2$ where $A,B,C$ are constants and $R_m$ stands for the radius of the tokamak machine, respectively. Determine the points of intersection of isocontours with the radial axis (i.e., $r_{\pm }=$?).