Wiggler radiation contains not only the usual component with short wavelength radiation but also a broadband component in the long wavelength region, which emits in the near forward direction, peaked at an angle 1/gamma. Firstly, spontaneous radiation from a wiggler is analyzed based on the basic formula of electrodynamics. With the long wavelength approximation, a formula for the long wavelength is obtained. The theoretical result is well coincided with the result of numerical calculation. Also the character of this radiation is analyzed. Secondly, the photon fluxes coming separately from the wiggler and a bending magnet are compared, for the wavelength longer than 1 mu m. The result shows the superiority of wiggler radiation in the infrared region. Finally, the long wavelength radiation from the wiggler is compared with the undulator transition radiation and the bending magnetic edge emission. The result shows that long wavelength radiation from the wiggler is the strongest one.
