Electrostatic discharge is a single, fast, high current transfer of electrostatic charge that results from :
• Direct contact transfer between two objects at different potential, (this is the case for human ESD), or
• A high electrostatic field between two objects when they are in close proximity (this is the case for ESD on spacecraft, in space).
Surface charging induced electrostatic discharge refers to the dynamic electronic current which leads to surface potential neutralization after the build-up of electric charge that occurs on exposed surfaces, due to particles from the external space environment, anywhere within or outside the spacecraft structure on exposed surfaces. Discharges can occur both on dielectrics (called surface-dielectric discharges or normal gradient electrostatic discharges) and also on conductors within or outside the spacecraft (called inverted voltage gradient discharge or metallic discharge). These are responsible for major hazards associated with satellite surface charging.
Similarly, internal charging induced electrostatic discharge lead to complete or partial neutralization of electric fields inside dielectrics or on internal conductors.