Magnetic Flux Ropes at Mars and Their Impacts on Heavy Ion Escape

Abstract

Flux ropes (FRs), ubiquitous helical magnetic structures in solar system plasmas, are important to energy and particle transport. At Mars, where global intrinsic magnetic fields are absent, FRs form through magnetic reconnection (MR) and magnetospheric or ionospheric boundary wave instabilities (BWIs), but their role in ion escape remains controversial. Here, we first present the global distribution of MR- and BWI-FRs from Martian ionosphere to magnetosheath, utilizing 4,012 FR events identified from 5-year observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite. We find that the global occurrence rate of FRs associated with BWIs is comparable with those from MR. Enhanced oxygen ion outflow fluxes and densities within most nightside BWI-FRs suggest they predominantly originate from the dayside ionosphere/magnetosphere. These BWI-FRs have sufficient magnetic field intensity to carry oxygen ions beyond escape energies, suggesting their potential role in facilitating global ion escape from Mars via magnetotail transport.