We report initial measurements from the ULECA sensor of the Max-Planck-Institut/University of Maryland experiment on ISEE-1. ULECA is an electrostatic deflection-total energy sensor consisting of a collimator, deflection analyzer and an array of solid state detectors. The position of a given detector, which determines the energy per charge of an incident particle, together with the measured energy determine the particle's charge state. We find tJ~at a rich variety of phenomena are operative in the transthermal energy regime (~10 keV/Q to -100 keV/Q) covered by ULECA. Specifically, we present observations of locally accelerated protons~ alpha particles, and heavier ions in the magnetoshoath and upstream of the Earth's bow shock. Preliminary analysis indicates that the behavior of these locally accelerated particles is most similar at the same energy per charge.
In this paper we present some preliminary results on charged particles near the Earth's bow shock based on measurements made with the ULE, CA sensor (Ultra Low Energy Charge Analyzer) of the HOM experiment on ISEE-1.
Figure 1 shows a schematic drawing of the ULECA sensor. It consists of three separate sub-sections, each of which consists of a collimator to focus incoming particles, high voltage plates to deflect the particles, mask slits to define their final deflection (and hence their energy per charge), and solid state detectors to measure their total energy. Discriminators for each detector allow one to separate H, He, and the charge group O > 3 using only the counting rate data. The heavy ions may be further resolved using pulse height analysis techniques.