The Helical symmetric reversed field configurations with minimum potential energy has been studied by applying the variational principles to the cylindrical plasma of finite plasma pressure.
The helical symmetric magnetic field with finite pressure gradient, which is derived from the MHD equilibrium equation, can't satisfy the condition of minimum potential energy obtained based on the Woltjer's invariance.
An axisymmetric RFP which satisfies the Woltjer's invariance, can only confine the pressure gradient plasma without destroying the MHD equilibrium.