Sensing the Tenuous Earth Ambient Plasma (TEAP) With Near Earth Radiation Detector (NERD) Networks: Regime Theory, Factorial Sensitivity Analysis, and Electrometer Front-End Limits

The charged component of Earth’s atmosphere forms one medium from the ionosphere to the ground, here named the tenuous Earth ambient plasma (TEAP). Above about 80 km TEAP responds collectively by oscillation; nearer the ground it responds only by relaxation, on a time scale set by its conductivity. This paper treats near-surface TEAP as a sensing problem for Near Earth Radiation Detector (NERD) networks, ground-based sensor networks of compact nodes mounted on street-light poles. A locality rule assigns each quantity either to the NERD node or to external feeds according to its spatial correlation length, and a detectability result shows that a signal common to all sites, such as space weather modulation of cosmic-ray ionization, can be recovered over land only by averaging many independent cells. Two full factorial design-of-experiments studies quantify the framework. A sea-level TEAP ion-balance model, run over 65 610 combinations of ten drivers read by NERD channels, shows that the aerosol sink explains 72% of the variance in small-ion concentration and potential gradient over land, that charged aerosol can outnumber small ions by more than three orders of magnitude, and that a daily solar detection at three standard deviations needs a median of 166 independent land cells but only 13 marine cells. A circuit-level study of the NERD electrometer front-end over 17 496 configurations shows that a guard ring removes every saturating configuration and that collection bias and air flow must be chosen together.