Plasma measurements with the retarding potential analyzer on Ogo 6

Abstract

The nature of the results from the retarding potential analyzer on Ogo 6 are described. The device appears to be capable of measuring ion temperature to an accuracy of better than 10% in a quiet ionosphere. In the dawn‐dusk plane the ion temperature is observed to vary from 1000° to 4000°K; the higher temperatures are associated with higher altitudes in the winter hemisphere. Molecular ions are detected near perigee (400 km), but their concentrations seldom exceed 1% of the O+ ion concentration. At midlatitudes and higher altitudes (>700 km) the lighter ions H+ and He+ are both present at approximately the O+ concentration, but their relative importance decreases near and in the polar regions. Both polar regions display large spatial fluctuations in ion concentration, and this behavior extends somewhat into the plasmasphere. Fluxes of electrons with energy greater than 10 ev of the order of 108 cm−2 sec−1 are observed; the fluxes change rather smoothly within the plasmasphere but show rapid and large variations at higher latitudes. The device also operates in a mode that examines the horizontal changes in ion concentration (fractional changes as small as 10−3 can be observed) with a spatial resolution from 350 to as small as 40 meters, depending on the telemetry rate.

Presunrise ion temperature enhancement observed at 600 km low‐ and mid‐latitude ionosphere

“…[2] The plasma temperature in the topside ionosphere has been measured with in-situ instruments onboard spacecraft for more than 30 years [Hanson et al, 1970;Heelis and Hanson, 1980;Oyama et al, 1996aOyama et al, , 1996bVenkatraman and Heelis, 1999]. Several theoretical models are also available to explain the plasma temperature variations [Bailey et al, 1973;Watanabe et al, 1995;Su et al, 1995;Balan et al, 1997].…”

The retarding potential analyzer aboard the satellite TAIYO.

“…The measurements of the plasma parameter by the RPA have been carried out with many satellites (see for example HANSON et al, 1970HANSON et al, , 1973SPENNER et al, 1974) and RDA'S may be utilized more and more in the future for these measurements.…”

High Power Ion Cyclotron Heating in the VASIMR Engine

“…Available plasma diagnostics include a triple probe, 32 and 70 GHz density interferometers, a bolometer, a television monitor, an H-α photometer, a spectrometer, neutral gas pressure and flow measurements, several gridded energy analyzers (retarding potential analyzer or RPA) 3,8,47,48,49,50,51,52,53 , a momentum flux probe, an emission probe, a directional, steerable RPA and other diagnostics 54 . Reciprocating Langmuir density interferometer are the primary plasma diagnostics.…”