HEPPA-MMI is an international working group to study the impact of energetic particle precipitation (EPP) on the atmosphere, an important solar-terrestrial coupling mechanism that is directly linked to solar variability.
HEPPA-MMI was established during the first HEPPA workshop held in Helsinki in May 2008. It brings together scientists working in the fields of atmospheric modeling on one hand and observational data analysis on the other hand. The objectives of HEPPA-MMI are
- to assess the ability of state-of-the-art atmospheric models to reproduce EPP-induced middle atmosphere composition changes,
- to identify and - if possible – remedy model deficiencies related to chemistry, dynamics, and ionization schemes,
- to serve as a platform for discussion between modelers and data producers.
This is achieved by dedicated case studies dealing with quantitative comparisons of observed and modeled species abundance during selected periods of pronounced particle forcing, as well as by inter-comparing the simulations performed by different models. A summary of past and ongoing HEPPA-MMI activities can be found in SPARC Newsletter No 36.
Recently HEPPA-MMI has been joined with the SOLARIS working group to form the SPARC activity SOLARIS-HEPPA - solar influences for SPARC. Both initiatives focus on modeling and understanding of the solar influence on climate through chemical and dynamical processes in the middle atmosphere, complementing each other by investigating different aspects of solar variability (particles vs. radiation). Common HEPPA-MMI & SOLARIS scientific goals have been recently defined.