A novel electromagnetic (EM) model was developed using the Plasimo platform with the aim to study different microwave induced plasmas. In this study, the EM model is coupled to the fluid non-local-thermal-equilibrium (non-LTE) description of a discharge (flow, temperatures and species densities), and it allows the construction of a 2D self-consistent multiphysics model for microwave induced plasmas. The surfatron is a well-known microwave plasma source for the production of surface wave sustained plasmas. The model is used to describe the plasma generated with this source and it permits, for the first time, the study of the differences between the plasma surrounded by the surfatron cavity, i.e. the inside plasma, and the plasma in front of it, i.e. the outside plasma. It also allows the study of the transition from diffusion controlled towards dominant volume recombination electrons losses regime, as is shown with the simulation results with pressure values changing from 660 to 8800 Pa for an argon plasma with a radius of 3 mm and a microwave frequency of 2.45 GHz. The modelling results are compared with experimental measurements of the electron density and temperature and an excellent agreement is found.