Laboratory simulation of the structure of disturbed zones around bodies in space

Abstract

Laboratory studies of some aspects of the spacecraft-space plasma interaction have been carried out to obtain information, not currently available from the in situ data, on the near and intermediate wake regions. Observations of ion flux densities in these regions downstream from a conducting spherical body indicate: 1. (1) the ion flux enhancement found in the wakes of conducting bodies apparently reaches a peak value at a location given approximately by r = S . R 0 (where S = V flow √2kT e/M + and R 0 = body radius) provided the body is at floating potential; 2. (2) the general dependence of the location of this peak value on S as well as ( eφ kT e ) supports the assumption that this effect results from a focusing mechanism; and 3. (3) the width of the downstream disturbance, although apparently non-linear in the near wake zone, was observed to be linear beyond the point S . R 0. Some preliminary data are given showing the structure of the disturbed flow field downstream from a model of the Apollo spacecraft. These data are found to differ in some aspects from data obtained from spherical bodies.