Plasma outflows, escaping from Earth through the high-altitude polar caps into the tail of the magnetosphere, have been observed with a xenon plasma source instrument to reduce the floating potential of the POLAR spacecraft. The largest component of H + flow, along the local magnetic field (30 to 60 kilometers per second), is faster than predicted by theory. The flows contain more O + than predicted by theories of thermal polar wind but also have elevated ion temperatures. These plasma outflows contribute to the plasmas energized in the elongated nightside tail of the magnetosphere, creating auroras, substorms, and storms. They also constitute an appreciable loss of terrestrial water dissociation products into space.

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Closed-loop control of composition and temperature during the growth of InGaAs lattice matched to InPWe examine the use of spectroscopic ellipsometry ͑SE͒ for fully automated, in situ real-time control of the barrier thickness for resonant tunneling diodes ͑RTDs͒ grown by molecular-beam epitaxy ͑MBE͒. The RTDs in this study utilize AlAs barriers, an InGaAs well with an InAs subwell, and lattice-matched InGaAs spacer layers, grown on an InP͑100͒ substrate. Pseudodielectric functions for the strained AlAs barriers were generated from SE data acquired during MBE growth, using simultaneous photoemission oscillation measurements for in situ thickness calibration. For closed-loop control, the measured dielectric functions were utilized in conjunction with a virtual substrate model to derive the instantaneous layer thickness from real-time SE data. Repeatability was tested by growing several series of AlAs barriers and complete RTDs under fully automated control, with shutter actuation based on the real-time thickness determined from SE. The results show that by using SE for real-time control, barrier thickness repeatability on the order of Ϯ0.1 ML can be achieved.

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