Observations of electron density and electron temperature during large scale magnetic fields in the dayside Venus ionosphere and lesson for Mars

We first present several dayside electron density (Ne) and electron temperature (Te) profiles observed by the Langmuir probe experiment aboard Pioneer Venus Orbiter when the Venus ionosphere was in a magnetised state and then examine the effect of large scale magnetic fields on the Venus ionosphere. We find that for the magnetised ionospheres, the "top" moves down to altitudes near 200 km and the ionopause layers with steep altitude gradients in Ne and Te start above this altitude. No significant change in electron density and electron temperature is seen within the ionosphere. Occasionally a second ionopause layer is also seen at higher altitudes and the ionospheric region between the two ionopause layers, which is seen to extend to altitudes up to 250 km, too does not indicate any significant change in Ne and Te for these cases. These results have direct relevance to Mars where large scale ionospheric fields have also been observed