We study the asymptotic behavior at low energy of scattering amplitudes in
two dimensional magnetic fields with compact support. The obtained result d
epends on the total flux of magnetic fields. It should be noted that magnet
ic potentials do not necessarily fall off rapidly at infinity. The main bod
y of argument is occupied by the resolvent analysis at low energy for magne
tic Schrodinger operators with perturbations of lang-range class. We can sh
ow that the dimension of resonance spaces at zero energy does not exceed tw
o. As a simple application, we also discuss the scattering by magnetic fiel
d with small support and the convergence to the scattering amplitude by del
ta-like magnetic field.