ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-29-987-2011 On the effect of IMF turning on ion dynamics at Mercury Delcourt D. C. 1 Moore T. E. 2 Fok M.-C. H. 2 LPP, UMR7648, CNRS – Ecole Polytechnique, Saint-Maur des Fossés, France NASA, Goddard Space Flight Center, Greenbelt, Maryland, USA 10 06 2011 29 6 987 996 Copyright: © 2011 D. C. Delcourt et al. 2011 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/29/987/2011/angeo-29-987-2011.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/29/987/2011/angeo-29-987-2011.pdf

We investigate the effect of a rotation of the Interplanetary Magnetic Field (IMF) on the transport of magnetospheric ion populations at Mercury. We focus on ions of planetary origin and investigate their large-scale circulation using three-dimensional single-particle simulations. We show that a nonzero <i>B</i><sub>X</sub> component of the IMF leads to a pronounced asymmetry in the overall circulation pattern. In particular, we demonstrate that the centrifugal acceleration due to curvature of the <b><i>E</i></b> × <b><i>B</i></b> drift paths is more pronounced in one hemisphere than the other, leading to filling of the magnetospheric lobes and plasma sheet with more or less energetic material depending upon the hemisphere of origin. Using a time-varying electric and magnetic field model, we investigate the response of ions to rapid (a few tens of seconds) re-orientation of the IMF. We show that, for ions with gyroperiods comparable to the field variation time scale, the inductive electric field should lead to significant nonadiabatic energization, up to several hundreds of eVs or a few keVs. It thus appears that IMF turning at Mercury should lead to localized loading of the magnetosphere with energetic material of planetary origin (e.g., Na<sup>+</sup>).

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