The ionospheres and magnetospheres of weakly magnetized bodies with substantial atmospheres (e.g. Mars, Venus, Titan, Pluto and comets) are subject to disturbances due to solar activities, interplanetary conditions, or parent magnetospheric environments (e.g. solar flares, coronal mass ejections and solar energetic particles), sharing similarities with their magnetized counterparts but with scientifically important differences. As an integral part of planetary atmospheres, ionospheres are tightly coupled with the neutral atmosphere, exosphere and surrounding plasma environment, possessing rich compositional, density, and temperature structures. The interaction among neutral and charged components affects atmospheric loss, neutral winds, photochemistry, and energy balance within ionospheres. This session invites abstracts concerning remote and in-situ data analysis, modeling studies, comparative studies, instrumentation and mission concepts for weakly magnetized solar system bodies. Topics such as dayside and nightside ionospheric characteristics and variability, ion-neutral coupling, and responses of the ionized and neutral regimes to transient space weather events are especially encouraged.