  We propose a model of a relativistic string formed by a scalar complex field,
acting as electromagnetic field source. An axiosymmetric solutions of the
stationary equations for the scalar and electromagnetic fields are found
numerically. The mass $m$ is calculated as a function of the charge $e$ and the
magnetic moment $\mu$ of the system. The resulting toroidal structure is
interpreted as an electron because the calculated ratio $e^3/(2mc^2\mu)$
coincides with the fine-structure constant $\alpha=e^2/(\hbar c)\approx
e^3/(2m_ec^2\mu_e)$.
