  Using the in-viscid two-field reduced MHD model, a new analytical theory is
developed to unify the Hahm-Kulsrud-Taylor (HKT) linear solution and the
Rutherford quasi-linear regime. Adopting a quasi-linear approach, we obtain a
closed system of equations for plasma response in a static plasma in slab
geometry. An integral form of analytical solution is obtained for the forced
magnetic reconnection, uniformly valid throughout the entire regimes from the
HKT linear solution to the Rutherford quasi-linear solution. In particular, the
quasi-linear effect can be described by a single coefficient $K_s\propto
S^{8/5} \psi_c^2$, where $S=\frac{\tau_R}{\tau_A}$ and $\psi_c$ are the
Lunquist number and amplitude of external magnetic perturbation, respectively.
The HKT linear solution for response can be recovered when the index
$K_s\rightarrow 0$. On the other hand, the quasi-linear effect plays a key role
in the island growth when $K_s\sim1$. Our new analytical solution has also been
compared with reduced MHD simulations with agreement.
