All spacecraft, once they exceed about 60 km in altitude during the day or around 80 km at night, are exposed to the charged particles of the space plasma environment. These particles interact with and are collected by the surface materials of a spacecraft and change the electric fields on and around it. Of the continuum of charged particles of all energies, those below 50 keV are generally regarded as plasma and are covered in this clause. Higher energy particles are covered in the radiation environment clause (clause 9).
Within the magnetosphere, plasma flows almost freely up and down magnetic field lines but only slowly across it. Hence, two spacecraft observe similar plasmas if they are on the same field line, even if far apart. These spacecraft share the same Lshell and magnetic local time.
A brief overview of the effects of the plasma environment is given in Annex H.2. Requirements for design, analysis and testing of spacecraft, concerning the effects of plasma on spacecraft systems are described in a parallel standard ECSS-E-ST-20-06 (Spacecraft Charging).