The Langmuir plate and spherical ion probe experiments aboard explorer XXXI

Abstract

Two probe experiments aboard Explorer XXXl measure the concentrations and tamperaturer of the thermal electrons and major ion species encountered by the satellite. A brief description of the instruments is given and examples of data are presented to illustrate special features which could be relevant when contrasting results with those from other experiments on Explorer XXXI or Alouette II. Comparison with data from the ionosonde aboard the latter provided information on the effective collecting area of the probes and the influence of the plasma sheath surrounding the satellite.

Electron and ion temperatures in the ionosphere

“…The use of probes based on Druyvesteyn's relation (4) has been described by Bowen et al [1964Bowen et al [ (a), 1964] and by Wrenn (1969). Small amplitude sine waves of two different frequencies in the audio range are applied to the probe, and the intermodulation component, which is proportional to B2 j P/' V2, is se lected by a tuned amplifier.…”

“…The latter carried a topside sounder and a cylindrical probe, whilst the former carried cylindrical and planar Langmuir probes operated in a dc mode, and a plane probe operated in an ac mode , Donle (1969), Wrenn (1969)] together with a plane ion trap operated in a dc mode and a spherical ion probe operated in an ac mode [Donley (1969), Wrenn (1969)]. …”

Electron temperatures in the wake of an ionospheric satellite

“…Another RPA, programed to make measurements on the composition, density, and temperature of the thermal positive ions, is placed on the satellite face opposite the electron RPA. Each ion measurement takes 1 s. The operational techniques of these experiments have been described formerly [Donley, 1969;Wrenn, 1969]. Donley et al [1969] have made a comparison between electron temperature values measured by the RPA and simultaneous values measured by the Langmuir plate.…”

Some implications of satellite spin effects in cylindrical probe measurements

“…Langmuir probe data have been found to contain periodic electron current variations in synchronization with a satellite spin cycle [Bourdeau and Donley, 1965;Samir and Willmore, 1965;Henderson and $arnir, 1967; Copyright ¸ 1972 by the American Geophysical Union. Wrenn, 1969]. The results were anticipated, since a planar Langmuir probe having its collecting surface oriented at 90 ø to a satellite's spin axis is expected to detect electron density variations that are a direct consequence of the probe's rotation through the satellite's wake structure.…”