Beatriz Sanchez-Cano
The ionosphere of Mars is the layer of its atmosphere where gases are separated into ions and electrons by solar radiation. The ionopause is the upper-most region where the ionosphere terminates. However, the Martian ionopause is not well-understood because it does not always form, and when it does, it is located over a large range of altitudes, varies rapidly and is highly structured. This poster shows a statistical analysis of the different parameters that play a role in ionopause formation at Mars. The study focuses on observations from the day-side of Mars, and analyses several datasets from the MAVEN and Mars Express missions. It is found that the ionosphere almost always contains magnetic fields within it, and that there is a pressure balance at its upper boundary (the ionopause) between the solar wind and the ionosphere. This study is important because it informs us about the interaction between the solar wind and the Martian plasma system, which is currently not well-understood.
My name is Beatriz Sanchez-Cano, and I'm currently a postdoc at the University of Leicester. This poster shows my latest piece of work about the formation and characterisation of the Martian ionopause.
This work has been done in collaboration with all the people that appears on this slide. Moreover, this paper has been recently published in the Journal of Geophysical Research: Space Physics, and can be downloaded using the QR code on the slide.
SLIDE 2:
The ionosphere of Mars is the layer of its atmosphere where gases are separated into ions and electrons by solar radiation. The ionopause is the upper-most region where the ionosphere terminates for unmagnetised planets, such as Venus, Mars or comets.
However, the Martian ionopause is not well-understood because it does not always form, and when it does, it is located over a large range of altitudes, varies rapidly and is highly structured.
The schematic on the right shows the solar wind-Mars plasma system interaction and the role of different pressures that are important for the ionopause formation, such as the solar wind dynamic pressure in blue, the different types of magnetic pressure in red, and thermal pressures in green.
The ionopause (black dashed line) is formed at the altitude where there is a balance of all these pressures.
SLIDE 3:
--Left part: The ionopause can be easily identified with the pink profiles with the electron density and electron temperature parameters, when the first has a drastic decrease at the same time that the second has a large increase. Below the ionopause, cold plasma dominates. Above the ionopause, hot plasma dominates.
In contrast, profiles with no ionopause (in blue), they do not show an apparent change with altitude.
--Right part: the dynamic (in blue), magnetic (in red), and thermal (in green) pressures are plotted here for cases with (left) and without (right) ionopauses. As can be seen, the ionopause is formed when the dynamic and thermal pressures are equal. However, for an ionopause to be formed, the dynamic pressure at the top of the ionosphere (or in the solar wind) has to be of the same order of the magnetic pressure of the ionosphere to be able to enter into the Martian system.
SLIDE 4:
Take home message:
--The electron temperature is a key factor for determining the location of the ionopause
--Mars’ ionopause is only formed when the solar wind dynamic pressure at the top of the ionosphere (or in the solar wind) is large enough to compete with the magnetic field pressure of the ionosphere
--In those cases, the ionopause clearly separates the shocked solar wind (hot plasma) found in the Martian plasma system from the planetary ionospheric plasma (cold plasma).
Thank you very much :)