The principal spacecraft engineering concerns caused by space plasmas in different regions are outlined in Table H-2. Some of the most significant effects are listed below.
Because of their higher mobility, electrons preferentially accumulate on exposed spacecraft surfaces, causing them to charge negatively. In hot plasmas in the 10keV range charging can reach hundreds or thousands of volts. Charging is however greatly mitigated by secondary electron emission and photoemission. In cold plasma (e.g. ionosphere) charging levels are generally very low, however, the high velocity of an orbiting spacecraft relative to ion velocity in this region leads to a plasma void in its wake. This can permit high-voltage surface charging to occur on wake surfaces during auroral crossings.
High plasma densities (such as found in the ionosphere) cause reflection of radio beams below a critical frequency, as well as refraction and scintillation. Hence this acts as a barrier to satelliteground communications and complicates satellite radar altimetry, satellite navigation systems and the radio tracking of satellites.
For high potential surfaces, in dense plasmas, ions and electrons are drawn to negative and positive regions respectively, allowing a current to flow through the plasma. This acts as a current drain on high voltage systems, such as solar arrays and can affects the spacecraft floating potential.
Ion impacts due to flowing plasma (such as the solar wind) can result in sputtering from surface materials. Although solar wind plasma is cold, the ions carry considerable kinetic energy, typically ~1 keV for protons and ~4 keV for He++.
Neutral spacecraft-generated atoms can be ionized by sunlight or chargeexchange with other ions, to create a lowenergy (<10 eV) ion population. These ions can be drawn to negatively charged surfaces and can cause surface contamination.
Further details on spacecraft-plasma interactions can be found in the ECSS-E-ST-20-06 (Spacecraft Charging) standard.