Mars MGS ER Magnetometer M.Acuna Mars Global Surveyor Electron Reflectometer (ER) data Mars plasma electron solar wind NASA/PDS NASA/GSFC NASA/PDS calibrated mars sw 2s 8s 1997/09/14 2006/10/11 PDS:PPI/FULLWORD-RES-MAG-V1.0 Electron flux ToDo dynamic_spectrum