New findings on the Martian ionosphere released (It's the TEC, dammit!):
The highest electron densities are found at an altitude of about 140 km, where extreme ultraviolet light from the Sun ionises the neutral atmosphere. Electron densities above this layer generally decrease with increasing altitude. A secondary layer, which occurs at approximately 120 km, is produced by "soft" X-rays from the Sun and associated impacts with energetic electrons.
The composition and behaviour of the Martian ionosphere also differ over time and according to their geographical location. Atomic oxygen ions are most common at higher levels, while molecular oxygen species are more common at lower altitudes. These changes are caused by large variations in the solar wind, atmospheric dynamics and composition, and by the patchwork pattern of the crustal magnetic field.
The data show that the top of the ionosphere can drop below 250 km, but occasionally rise above 650 km. Graphs showing the vertical electron density of the ionosphere's main layer sometimes have a sharply pointed, flat or wavy shape, in contrast to its usual smooth, curved shape.
A broad increase in electron density is sometimes detected at 160-180 km, while a narrow layer of raised electron density is sometimes found in localised, but strongly magnetised regions, and an additional layer is occasionally present between the two main layers.
"These observations show that the Martian ionosphere is a lot more variable than I expected," said Paul Withers
of Boston University, lead author of the two papers. "Many of these features have not been predicted and it will be interesting to see how theorists attempt to explain them."
More info here:
[link to www.marsdaily.com