This work describes a combined experimental and numerical study of a low pressure argon plasma in a cylindrical magnetron reactor. The plasma properties are first investigated experimentally using optical emission spectroscopy as a function of the position in the reactor and the applied power, for two excitation modes (pulsed direct current and pulsed bipolar) at a constant pressure of 10 Pa. Langmuir probe measurements are also performed to complement the plasma diagnostic. The results are compared with three-dimensional particle-in-cell simulations combined with a Monte Carlo Collision scheme. A consistent agreement occurs between the experimentally measured and numerically calculated electron temperatures, enabling one to validate the numerical model and to explain the influence of the magnetic field on the spatial variations of the electron temperature. The aim of this work is to pave the way for more complex simulations, such as the modeling of a plasma enhanced chemical vapor deposition process. In a future article, we will investigate both experimentally and numerically the plasma polymerization of cyclopropylamine in the same reactor.