The magnetic field effect on measurements of electron density and temperature by cylindrical probes in the earth ionosphere

In 1960-70, cylindrical Langmuir probes were applied due to relative simplicity in their production. They were used in the USSR both at satellites (Cosmos-378, Intercosmos-2, -4, -8, 10, -19) and in experiments in vertical launches of rockets using the program Intercosmos (Vertical-4, -6, -10) for measurements of electron density and temperature. First these measurements were made in the middle latitudes. With increasing inclination of an orbit of launched satellites (satellites had no stabilization), falling sections could sometimes be observed on probe characteristics in the saturation current region. The satellite Intercosmos-Bulgaria-1300 stabilized along three axes was launched in 1981. It had a cylindrical probe, the longitudinal axis of which was constantly oriented down to the Earth. This satellite allowed definite conclusions concerning the geomagnetic field effect on a probe characteristic form and hence on determination of electron density and temperature. Examples are given of probe characteristics with falling sections. These measurements are compared with those performed in the laboratory plasma. Appearance of negative sections on probe characteristics is shown to be due to the geomagnetic field effect. The degree of this effect depends both on the electron density and temperature and on the voltage across the probe.