  Magnetic reconnection (MR) is considered as a major source of particle
energization in astrophysical plasma. In the past, analysis of MR often assumes
the magnetostatic condition, i.e. $\partial_t = 0$. We show that under the
Sweet-Parker-Petschek framework, steady state is an over-constraint and is not
achievable. On the other hand, the quasi-steady state defined as $\partial_t
\mathbf{E} = 0$ but $\partial_t \mathbf{B} \neq 0$ or equivalently
$\partial_t\mathbf{j}\neq 0$ better describes the asymptotic behaviour of MR
without turbulence. The upper limit of MR rate for quasi-steady MR is found to
be $\sim 1/3\sqrt{3} \sim 0.19$. The limit does not apply to impulsive or
turbulent MR of which $\partial_t\mathbf{B} \neq 0$ and $\partial_t\mathbf{E}
\neq 0$. In impulsive MR the rate can be higher or lower than 0.19 depending on
the state of the turbulence. Our results may explain the apparent discrepancy
in observations of solar flare MR rates. The analysis is independent of mass
ratio and thus the results are applicable to pair plasma.

Space Physics;Earth and Planetary Astrophysics;High Energy Astrophysical Phenomena;Solar and Stellar Astrophysics;Plasma Physics