The international working group Solaris-Heppa was founded 2012 by the merging of the working groups SOLARIS and HEPPA (High-Energy Particle Precipitation into the Atmosphere). It is part of the WCRP project APARC. The goal of Solaris-Heppa is to better understand and quantify the solar influence on the climate system, with a focus on chemical and dynamical processes in the middle atmosphere and their coupling to surface climate. We use composition climate models, mechanistic models, and satellite observations, and also provide state-of-the art solar forcing data for coordinated composition-climate model experiments (e.g., for CMIP7).