Study by Mars Express of the Response of the Martian Ionosphere to a Strong CME Directly Detected by MAVEN on March 8th, 2015

Abstract:

This study summarizes the effects of a strong coronal mass ejection (CME) on Mars as detected by Mars Atmosphere and Volatile Evolution Mission (MAVEN) in the solar wind and by Mars Express (MEX) in the nightside ionosphere. The Solar Wind Ion Analyzer (SWIA) onboard MAVEN identified a strong CME on March 8^th, 2015, characterized by an increase in the solar wind density and solar wind speeds up to about 800 km/s. Simultaneously with the MAVEN observations, the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on MEX detected unusually high local electron density and local magnetic field values in the nightside Martian ionosphere. The Ion Mass Analyzer (IMA) on Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) instrument, also on MEX, saw a sharp CME front followed by an increase in the ion speed and a sharp enhancement in the electron flux seen by the ASPERA-3 Electron Spectrometer (ELS) signals the CME. ASPERA-3 data also suggest an increase in the plasma temperature when the shock hits Mars. Finally, the peak ionospheric density obtained with MARSIS remote sounding exhibits a discrete enhancement over a period of about 30 hrs around the same latitude and local time. We believe that this high density ionospheric plasma is forced by the CME from dayside to the nightside towards high altitudes.