About the Reliability of Particle in Cell Methods and the Notion of a“Local”Temperature of Ionized Species Around a Spacecraft in the Ionosphere

The development of space science has generated important computer codes for the simulation of the interaction between complex space structures(artificial satellites,solar panels,etc.)and the surrounding plasma.The basic equation to be solved is the Poisson equation for the electric potential around a structure.Here,we try to study analytically the shadowing effect of a spacecraft on an electrode for the electron number density and the electron temperature.We suggest that the electron temperature should be taken as a variable and not as a parameter.However,its computation involves the knowledge of the histogram of the distribution of the frequencies of the electron velocities inside the computational cells.Also,we have illustrated the possibilities of artefacts due to the design and geometry of scientific instruments for the measurement of the electron number density and the electron temperature in the ionosphere.We suggest an optimal design for an electrode and its guard ring.