Accession Number : ADA215062

Title :   Radiation of Plasma Waves from Large Space Structures in Low Earth Orbit.

Descriptive Note : Final rept. 30 Jun 86-31 Aug 88,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE CENTER FOR SPACE RESEARCH

Personal Author(s) : Hastings, D. E. ; Barnett, A. ; Olbert, S.

Report Date : 05 OCT 1988

Pagination or Media Count : 39

Abstract : There are many situations of interest in space and astrophysics which consist of a conducting body moving across a magnetized plasma. It is well known that large conducting objects which move slowly across magnetic field lines radiate low frequency (Alfven) waves. The interaction between a plasma and a moving conductor is studied to estimate the total power radiated at all frequencies. Toward this end, a formalism which permits us to compute the response of the plasma to an external current source. An integral equation is derived which relates the source current to the electrical properties of the conducting body. Radiation is produced at all frequencies for which one of the plasma modes has zero phase velocity in some direction. The mechanism by which this radiation is produced is analogous to Cherenkov radiation. Large conducting space structures in low Earth orbit will have a non-negligible motionally induced potential across their structures. The induced current flow through the body and the ionosphere causes the radiation of Alfven and lower hybrid waves. A space station-like structure and tether are studied. For the space station structure the radiation impedance is particularly high for frequencies in the tens of kilohertz range, which suggests that the space station may be an efficient source of lower hybrid waves. The tether is also shown to be a generator of VLF waves. The implications for these two structures are discussed. (jhd)

Descriptors :   *PLASMA WAVES, *RADIATION, *SPACE STATIONS, ASTROPHYSICS, EARTH ORBITS, EFFICIENCY, ELECTRICAL PROPERTIES, ELECTRICAL IMPEDANCE, INDUCED ENVIRONMENTS, INTEGRAL EQUATIONS, IONOSPHERE, LOW FREQUENCY, LOW ORBIT TRAJECTORIES, MAGNETIC FIELDS, MAGNETIZATION, PLASMAS(PHYSICS), SOURCES, SPACECRAFT, VERY LOW FREQUENCY.

Subject Categories : Atmospheric Physics
      Plasma Physics and Magnetohydrodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE