Penetrating Solar Wind Protons Drive Asymmetric Acceleration of Oxygen Ions in the Martian Magnetotail Current Sheet

We investigate the asymmetric energy distribution of outflowing heavy ions in the Martian magnetotail current sheet by combining observations by Tianwen-1 and Mars Atmosphere and Volatile Evolution (MAVEN) satellites with global multifluid magnetohydrodynamic (MHD) simulations. Tianwen-1 observed energetic oxygen ions, solar wind protons, and magnetic-field lines bending toward the equatorial plane in the current sheet. Constrained by MAVEN upstream observations, simulations show that solar wind protons deflect opposite to the convection electric field to maintain momentum conservation during heavy ion pickup, dragging magnetic-field lines to form a sinking topology in the current sheet. Downtail, protons penetrate deeper in the current sheet, generating strong localized motional and Hall electric fields in the +E (aligned with the convection electric field) hemisphere, which can accelerate ions to keV energies. Statistical analysis further confirms that the sinking magnetic-field topology is persistently accompanied by asymmetric acceleration. Our study identified a new pathway for the solar wind proton entry into the magnetotail, which drives heavy ion asymmetric acceleration in the current sheet, a pathway possibly common in induced magnetotails.