Planetary Science

Martian Minimagnetopause

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Science  12 Dec 2003:
Vol. 302, Issue 5652, pp. 1863
DOI: 10.1126/science.302.5652.1863b

The solar system is not as empty as it may seem; the space between the planets is permeated with an interplanetary magnetic field (IMF) and bombarded continuously by the solar wind. When the IMF and the solar wind intersect at a planet, even a small planet like Mars (with a thin atmosphere, weak magnetic anomalies, and a paltry plasmasphere/ionosphere), the magnetic field lines are compressed and pile up, and the solar wind particles interact with the planet.

Harnett and Winglee have developed a three-dimensional, non-ideal magnetohydrodynamic model of the magnetic pile-up and particle interactions. The simulations show the formation of a minimagnetopause above the magnetic anomalies in the southern hemisphere of Mars. The minimagnetopause keeps the solar wind from reaching the Martian surface, it demagnitizes ions, and it increases the size and magnitude of the magnetic field and current. The minimagnetopause only appears on the dayside and is caused by the relatively stronger magnetic anomalies in the southern hemisphere. This previously unrecognized and asymmetric interaction may change our understanding of the Martian environment, particularly whether hydrogen and oxygen remain neutral species in the Martian exosphere or exchange with interplanetary space. — LR

Geophys. Res. Lett. 10.1029/2003GL017852 (2003).

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