Pair production in a time-dependent magnetic field

The production of electron-positron pairs in a time-dependent magnetic fiel d is estimated in the hypotheses that the magnetic field is uniform over la rge distances with respect to the pair localization and it is so strong tha t the spacing of the Landau levels is larger than the rest mass of the part icles. This calculation is presented since it has been suggested that extre mely intense and varying magnetic fields may be found around some astrophys ical objects.