tokens: For worst case auroral charging assessments , a thermal ion density of 125 cm-3 and temperature 0,2 eV shall be used . NOTE This low ion density comes from a severe charging case seen on the DMSP spacecraft by [ RD.9 ] . Measuring ionospheric thermal ion density during a strong charging event is potentially prone to errors because of the way the charged satellite alters ion trajectories , so there is a degree of uncertainty in this measurement .