Dual-Spacecraft Observation of Density Features in the Near-Terminator Martian Ionosphere: Mars Express Ionospheric Sounding and MAVEN

David DeWitt Morgan1, Donald A Gurnett2, Paul R Mahaffy3, Jasper S Halekas4, Rudy A Frahm5 and John E P Connerney3, (1)University of Iowa, Department of Physics and Astronomy, Iowa City, IA, United States, (2)University of Iowa, Physics and Astronomy, Iowa City, IA, United States, (3)NASA Goddard Space Flight Center, Greenbelt, United States, (4)University of Iowa, Iowa City, IA, United States, (5)Southwest Research Institute, San Antonio, TX, United States