Magnetic and electrostatic fluctuations are measured in the CASTOR tokamak with a reasonable spatial and temporal resolution to better understand the nature of turbulent processes in tokamaks. We have found that the broadband magnetic fluctuations in the plasma core are nearly independent of the safety factor q(a). However, their level is dramatically reduced (by a factor of three) when the aspect ratio increases from 5.4 to 6.6. The character of electrostatic structures in the edge plasma was found to be quite similar to that observed in large tokamak experiments. Furthermore, the fluctuations of the longitudinal current have been identified in the scrape-off layer. These fluctuations might represent a link between the magnetic and electrostatic components of plasma turbulence in this region.