National Academies Press: OpenBook

Plasma Science: From Fundamental Research to Technological Applications (1995)

Chapter:Vehicle-Environment Interactions

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Suggested Citation:"Vehicle-Environment Interactions." National Research Council. 1995. Plasma Science: From Fundamental Research to Technological Applications. Washington, DC: The National Academies Press. doi: 10.17226/4936.

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SPACE PLASMAS 111 a subsatellite, or on the ground. Objectives include the study of antenna properties, near-zone electromagnetic field studies, wave propagation, and wave-particle interactions. Ground-based HF wave (megahertz-range) injections are launched from powerful radars into the ionosphere under quiet conditions, during magnetic storms, or in conjunction with chemical releases from active experiments. A large number of plasma processes can be studied in this way: focusing or defocusing of the beam, interference with communications, heating of the plasma, generation of suprathermal electron fluxes and airglow, instabilities including self-focusing, parametric interactions and strong Langmuir turbulence, generation of plasma irregularities, focusing by chemical releases, and effects of a hierarchy of heater thresholds. In addition, pulsed HF heating is used to modulate the auroral electrojet current for extremely low frequency (ELF) or VLF wave generation. VLF wave experiments study wave-induced particle precipitation, earth-ionosphere wave guide modification, stimulation of VLF emissions, direct D-region heating, and ELF-modulated VLF to produce a polar electrojet antenna. Strong acoustic waves from explosions generate gravity waves and acoustic shock waves that couple into the plasma through collisional interaction. Vehicle-Environment Interactions A space vehicle perturbs the environment in a number of ways. Out-gas clouds, fluid dumps, and thruster firings interact with the ambient plasma much as the neutral gas injections described above. In addition, the structure itself creates a wake in the plasma, in particular for orbiting platforms, for which the spacecraft velocity generally is larger than the ion thermal velocity. Surface glow induced by neutral atmosphere interactions with the spacecraft surface has been studied in the case of the space shuttle. High-voltage power systems and their interaction with the ionosphere were studied in sounding rocket experiments. Objectives were to study the plasma sheath, the charging levels, and the steady-state currents in the ambient plasma. Processes associated with the physical contact between plasmas and exposed surfaces in space are an important practical aspect of many advanced scientific and technological space systems. For example, the ability to draw electron current from magnetized space plasmas is an essential feature of plans for power-producing electrodynamic tether systems. Charging of dielectrics in the vicinity of high-current beam experiments is similarly an important concern. It is striking to realize that while basic issues of plasma sheaths and current extraction have been known for more than 50 years, we still lack fundamental knowledge of the processes involved, especially at high voltages and currents. Relatively simple experiments, such as measuring the voltage-current collection curves for magnetized plasma, have yet to be done for ranges of parameters in which large-amplitude plasma waves play an important role.

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Plasma science is the study of ionized states of matter. This book discusses the field's potential contributions to society and recommends actions that would optimize those contributions. It includes an assessment of the field's scientific and technological status as well as a discussion of broad themes such as fundamental plasma experiments, theoretical and computational plasma research, and plasma science education.

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