Low‐Resource Technique for Measurement of H+ and O+ in the Terrestrial Magnetosphere.

Measurement of O+ in the Earth's magnetosphere is important for monitoring and understanding the initiation and evolution of geomagnetic activity. During active times, O+ can be the most abundant ion in the magnetosphere. Furthermore, because O+ and H+ damage exposed spacecraft materials through different processes, measurement and prediction of O+ and H+ fluxes is critical for understanding cumulative damage effects to these materials resulting from the ambient plasma environment of a spacecraft. We describe a simple technique for quantitative, in situ measurement of O+ and H+ fluxes using ultrathin foils. This technique is a low‐resource addition to a standard electrostatic energy‐per‐charge analyzer followed by an array of detectors. H+ and O+ abundances up to a few tens of keV can be determined by comparison of counts in detectors having no ultrathin foil at the detector aperture, in which both H+ and O+ are detected, and adjacent detectors having a foil over the aperture of the appropriate thickness to stop the transmission of O+ but through which H+ can transit. We describe three techniques for implementing this method enabling differentiation of O+ and H+ in an instrument package significantly simpler than traditional mass spectrometers. Plain Language Summary: Measurement of oxygen ions in near‐Earth space is important for monitoring and understanding the current state of the magnetosphere. While hydrogen is typically the most abundant ion in the magnetosphere, during times of enhanced geomagnetic activity oxygen can dominate. Additionally, oxygen and hydrogen ions can damage exposed spacecraft materials by species‐dependent processes. Thus, measurement and prediction of oxygen and hydrogen fluxes is critical for understanding cumulative damage effects to spacecraft materials as well as determining magnetospheric activity levels. We describe a simple, low‐resource technique for measuring oxygen and hydrogen fluxes in the spacecraft's local plasma environment. This concept utilizes standard measurement techniques for energy selection followed by an array of detectors. The concept uses two types of detectors: one covered with an ultrathin foil and one with no foil. The detector with the foil will measure hydrogen only, as the foil is specifically tuned to prevent oxygen transmission. The detector with no foil measures both oxygen and hydrogen. The abundances of oxygen and hydrogen can be determined by comparison of counts in the two detector types. We describe three techniques for implementing this method enabling differentiation of oxygen and hydrogen in an instrument package significantly simpler than traditional mass spectrometers. Key Points: Measurement of magnetospheric H+ and O+ is critical for understanding dynamics and energization processesA novel application of ultrathin foils enables low‐resource detection of magnetospheric H+ and O+Three implementation schemes of this low‐resource measurement technique are presented, with one scheme already successfully on‐orbit [ABSTRACT FROM AUTHOR]