Abstract

REYES-RUIZ, M.; ACEVES, H.  and  PEREZ-DE-TEJADA, H.. On the origin of the tailward velocity of O⁺ ions over the magnetic poles of Mars. Rev. mex. astron. astrofis [online]. 2010, vol.46, n.1, pp.135-144. ISSN 0185-1101.

We numerically simulate the dynamics of a population of O⁺ ions of ionospheric origin picked-up by the solar wind in the dayside ionosheath of Mars. Their average velocity as they reach the magnetic polar regions of the planet is compared with in situ measurements of the Mars Express spacecraft. We find that the velocity of O⁺ ions measured over the magnetic poles of the planet, which is essentially tailward with very small y and z-components according to measurements, cannot be accounted for solely in terms of particle gyromotions. We suggest that the velocity of O⁺ ions over the magnetic poles of the planet is more probably the result of wave-particle interactions that mediate the transfer of momentum from the solar wind plasma to ionospheric plasma and newly born ions in the ionosheath.

Keywords : planets and satellites: individual (Mars); plasmas; solar wind.