Ionospheric Langmuir Probe Electron Temperature Asymmetry and Magnetic Field Connectivity

What is it about?

This paper proposes an explanation of the electron temperature asymmetry measured with the Planar Langmuir Probe (PLP) on the CHAMP satellite. In summary the electron measured at a given latitude appeared to be systematically different, depending on whether the spacecraft was northbound or southbound. The explanation proposed in this paper has to do with "magnetic connectivity" of the PLP with other parts of the satellite. For example at mid latitudes in the Northern emisphere, with a normal flying attitude, Earth magnetic field lines going through the CHAMP PLP do not intercept other parts of the satellite if the satellite is northbound, but they do if the satellite is southbound. The relatively small electron gyro-radii, and the fact that on the scale length of the satellite, electrons are confined to magnetic flux tubes, results in distorted electron distribution functions at the PLP is magnetically connected to the satellite boom. These distortion in turn account for the observed temperature differences qualitatively and quantitatively.

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Why is it important?

The statistically systematic asymmetry in electron temperatures had been noticed and reported in the literature (Rother, et al. DOI: 10.1029/2010RS004445), but never explained. This remained a small mystery in the space physics community until the publication of this article.