This paper presents an electromagnetic noise source approximation method based on a 2-D array of electric dipoles for use in finite-difference time-domain simulations. The currents (both magnitude and phase) of these dipoles are optimized via a particle swarm algorithm so as to minimize the difference between the magnetic near-field produced by the dipole array and the magnetic near-field produced by the device under test. The method presented requires only the magnitude of the magnetic field to be measured, simplifying the measurement process. The new noise source modeling method has been applied to a transmission-line test case, demonstrating the performance and accuracy of the method.