Speakers
Description
After crossing the bow shock and entering the magnetosheath, the solar wind experiences substantial modifications: plasma
temperature, magnetic field strength, and particle density increase significantly, while the flow velocity decreases and its
direction is deflected. Magnetohydrodynamic (MHD) theory provides quantitative predictions for the changes in these
plasma parameters across the shock transition. The THEMIS spacecraft constellation, operating on comparable orbital
trajectories, offers an excellent platform for testing these MHD bow shock jump conditions through in situ magnetic field
and ion plasma observations. In this study, we investigated two events on 26 July 2007 and 2 September 2007, during which
one THEMIS spacecraft was located upstream of the bow shock in the pristine solar wind, while another spacecraft was
simultaneously positioned downstream within the magnetosheath. For both events, average values of plasma density,
magnetic field magnitude, and solar wind velocity were determined on either side of the shock. Shock normal vectors were
calculated using both Minimum Variance Analysis (MVA) and coplanarity techniques, applied consistently to the same
upstream and downstream intervals. Subsequently, the downstream-to-upstream ratios of magnetic field strength and solar
wind velocity were derived and compared with theoretical expectations.
Our results show good agreement with the Rankine–Hugoniot relations for both events, within the uncertainties associated
with the measurements.