Ionospheric conductivities at planets and planet-like bodies without internal magnetic field

Based on Cassini measurements during 17 Titan flybys w have identified an ionospheric region ranging from 1450 km ± 95 km (approximately the location of the exobase) to approximately 1000 km where electrical currents perpendicular to the magnetic field may become important. In this region the ionosphere is highly conductive with peak Pedersen conductivities of 0.002- 0.05 S/m and peak Hall conductivities of 0.01-0.3 S/m depending on Solar illumination and magnetospheric conditions. However, Hall and Pedersen conductivities depend strongly on the magnetic field magnitude, which is highly variable, both in altitude and with respect to the draping configuration of Saturn’s magnetic field around Titan. Furthermore, resulting from a decreasing magnetic field with decreasing altitude, a consistent double peak nature is found in the altitude profile of the Pedersen conductivity, where the lower conductive region is typically more intense. In a similar way we also analyse magnetic altitude profiles and electron density profiles through the dynamo region on Mars, where a similar but weaker magnetic field structure exists for some solar wind conditions. On Mars the temporal and spatial development of ionospheric conductivities appears to be very complicated. This complex nature of the Pedersen conductivity profile should give rise to very interesting ionospheric-“magnetospheric” coupling at planetary bodies without internal magnetic fields.