  Why adding a collinear magnetic field to the electric one on a D3 brane in a
system of two parallel separated D3 branes can enhance the open string pair
production? How is the open string pair production rate related to the QED ones
in the weak field limit? We answer these questions and report the somehow
expected but still remarkable relation between the weak field non-perturbative
stringy rate and the corresponding QED ones in this letter.
