Electrodynamics: Electron Emission, Ionization and Thermo-electric Thruster Systems

When the difference in electric potential between electrodes with different charge is high enough, an electric discharge through the fluid medium separating the electrodes occurs. The resulting electric flux is associated with a local motion of electrons, the only mobile charge carrier inside the solid electrodes. As a result from the motion of electrons and the collisions and resistance forces inside the conducting electrodes, a local temperature increase occurs. The resistance against electron motion in fluid media is a result from similar forces. The biggest difference lies in the mobility of the charge carrier phase molecules. As in the solid electrodes, the electric conduction through a fluid phase leads to a local heating. Furthermore, higher temperature values increase the mean free path of the particles and reduces the electric resistance of the fluid. This region is characterized by the appearance of an electric arc.

The conductivity of electron inside the different charge conductors is described by the field of electrodynamics. The local change in the electron velocity in the interface region of the conductors is a research field of special interest. The characteristics of this region are responsible for the acceleration of electrons towards the region with lower electric resistance. The regions where very high absolute acceleration values are reached are called „Sheath layer“. In the „Sheath layer“, the macroscopic discharge reaches its maximum.

The modeling of the electron transport inside fluid media deals with the collisions between electrons and the neutral particles of the carrier phase. If the kinetic energy of the electrons exceeds the ionization energy of the carrier phase, the ionization process is initiated and plasma is generated.