Ambipolar Electric Field in the Martian Ionosphere: MAVEN Measurements

The altitude and the local solar time dependence of the electron pressure and the resulting ambipolar electric field in the Martian ionosphere have been investigated by utilizing the electron density and temperature measurements obtained by the Langmuir Probe and Waves instrument aboard the Mars Atmosphere and Volatile Evolution mission (MAVEN) spacecraft. The magnitude of the ambipolar electric field is estimated to be 1–2 μV/m on the dayside—producing, on average, a total potential drop of up to 800 mV below 600 km. These calculations, when combined with the previous understandings on the significance of the Poynting flux in the Martian ionosphere, suggest that the ambipolar electric field and the Poynting flux are equally important in establishing a steady state in which the ions are transported from below the exobase to higher altitudes.