**Abstract**I will discuss the onset of the classical magnetohydrodynamic (MHD) tearing instability (TI) and focus on non-modal (transient) growth rather than the tearing mode. With the help of pseudospectral theory, I will demonstrate that the operators of the linear equations are highly non-normal, resulting in the possibility of significant transient growth at the onset of the TI. This possibility increases as the Lundquist number S increases. In particular, I will show evidence that the maximum possible transient growth, measured in the L2-norm, for the classical setup of current sheets unstable to the TI, scales as O(S1/4) on time scales of O(S1/4) for S≫1. This behaviour is much faster than the time scale O(S1/2) when the solution behaviour is dominated by the tearing mode. The size of transient growth obtained is dependent on the form of the initial perturbation. I will decribe the form of the optimal initial conditions for the maximum possible transient growth. Further, I will examine how the structure of the eigenvalue spectrum relates to physical quantities.

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