Abstract
Abstract
The Venusian interaction with the solar wind leads to the formation of an induced magnetosphere structured by plasma boundaries. Their dynamics is complex, due to the combined influence of external (solar photons, solar wind plasma, and interplanetary magnetic field, IMF) and internal (ionized atmosphere) drivers. Studying these drivers helps understanding of the transfer of energy and momentum throughout the Venusian system, and has thus implications for the erosion of the atmosphere through its coupling with the solar wind. We here analyze and rank the influence of the main drivers of the Venusian bow shock and ion composition boundary locations. We revisit the results of C. Signoles et al. based on Venus Express measurements by combining several methods such as the Akaike Information Criterion, Least Absolute Shrinkage Selection Operator regression, and partial correlations. These methods allow us to investigate cross correlations that appear and can bias the interpretation, and allow us to rank drivers with robust approaches. The bow shock appears primarily driven by the IMF intensity or Mach number, the IMF
θ
bn
angle separating quasi-perpendicular versus quasi-parallel shocks, and then the solar extreme-ultraviolet fluxes and solar wind dynamic pressure (with little influence of the convective electric field induced asymmetries). The ion composition boundary is primarily driven by extreme-ultraviolet fluxes, with a more reduced influence of several solar wind parameters and IMF induced magnetic pileup asymmetries. We also compare the behaviors of both boundaries and then compare the bow shock driver rankings at Mars and Venus. Finally we propose an analysis of the drivers of the extreme bow shock and ion composition boundary excursions.