On every terrestrial planet with an atmosphere, EUV radiation creates ions in the upper atmosphere that may flow upward. If the ions are energized enough, they can escape the gravitational potential. Depending on the presence and nature of the planetary magnetic field, there may be many different mechanisms causing ion upflow and outflow, like particle precipitation in auroral regions, ambipolar electric fields driving a polar wind, wave-particle interactions, direct solar wind-ionosphere interactions, etc. A fraction of these outflowing ions escapes into interplanetary space, so that they contribute to the erosion of the atmosphere; another fraction of ions may remain trapped inside the magnetosphere for some time, where they can affect the magnetospheric dynamics, especially for heavy ions, like O⁺; yet another fraction may return to the ionosphere. The magnetospheric dynamics can in turn affect the ionospheric outflow. This session invites contributions concerning all the processes controlling ionospheric ion upflow and outflow on Earth, Venus, and Mars, and their possible implications. Submissions comparing the processes at different planets, similarities and differences, are encouraged.