  This White Paper outlines the importance of addressing the fundamental
science theme <<How are charged particles energized in space plasmas>> through
a future ESA mission. The White Paper presents five compelling science
questions related to particle energization by shocks, reconnection,waves and
turbulence, jets and their combinations. Answering these questions requires
resolving scale coupling, nonlinearity and nonstationarity, which cannot be
done with existing multi-point observations. In situ measurements from a
multi-point, multi-scale L-class plasma observatory consisting of at least 7
spacecraft covering fluid, ion and electron scales are needed. The plasma
observatory will enable a paradigm shift in our comprehension of particle
energization and space plasma physics in general, with very important impact on
solar and astrophysical plasmas. It will be the next logical step following
Cluster, THEMIS and MMS for the very large and active European space plasmas
community. Being one of the cornerstone missions of the future ESA Voyage
2035-2050 science program, it would further strengthen the European scientific
and technical leadership in this important field.
