Jean Lilensten works in ionospheric physics, modelling the electron transport in the upper atmosphere. Jean discovered that the nightglow (including aurora) is polarized, and devotes most of his research to dig through in order to deduce what parameters can be deduced from the polarization parameters. Jean is co-Editor in Chief of the Journal of Space Weather and Space Climate, chair of the space weather and space climate international medals, and member of the program committee of the European Space Weather Week, a meeting that Jean contributed to create with a full bunch of colleagues and friends.