Ionospheric Langmuir Probe Electron Temperature Asymmetry and Magnetic Field Connectivity

Simulation results are presented, which demonstrate the effect of magnetic field orientation on electron temperature inferred from a planar Langmuir probe (PLP) near a physical object. PLP characteristics are calculated with two orientations of the magnetic field corresponding to: 1) magnetic field lines intersecting the PLP, also intersecting a physical object, and 2) field lines intersecting the PLP not intersecting any other physical object. In the first case, the PLP is referred to as being “magnetically connected” to another object, while in the second case it is “magnetically disconnected”. Characteristics computed for the PLP in these two cases are used to infer the electron temperature obtained using otherwise identical plasma parameters (electron and ion density and temperature, plasma flow velocity). Applying the same equation to fit the characteristics as derived by Rother et al. for the CHAMP PLP, the fitted electron temperature is found to be significantly lower when the magnetic field is oriented so as to magnetically connect both the probe and a physical object. This in turn is consistent qualitatively with the reported asymmetry in the electron temperature inferred from CHAMP's PLP between the northbound and southbound legs of the orbit at midlatitudes [1].