  How the solar wind influences the magnetospheres of the outer planets is a
fundamentally important question, but is difficult to answer in the absence of
consistent, simultaneous monitoring of the upstream solar wind and the
large-scale dynamics internal to the magnetosphere. To compensate for the
relative lack of in-situ data, propagation models are often used to estimate
the ambient solar wind conditions at the outer planets for comparison to remote
observations or in-situ measurements. This introduces another complication: the
propagation of near-Earth solar wind measurements introduces
difficult-to-assess uncertainties. Here, we present the Multi-Model Ensemble
System for the outer Heliosphere (MMESH) to begin to address these issues,
along with the resultant multi-model ensemble (MME) of the solar wind
conditions near Jupiter. MMESH accepts as input any number of solar wind models
together with contemporaneous in-situ spacecraft data. From these, the system
characterizes typical uncertainties in model timing, quantifies how these
uncertainties vary under different conditions, attempts to correct for
systematic biases in the input model timing, and composes a MME with
uncertainties from the results. For the case of the Jupiter-MME presented here,
three solar wind propagation models were compared to in-situ measurements from
the near-Jupiter spacecraft Ulysses and Juno which span diverse geometries and
phases of the solar cycle, amounting to more than 14,000 hours of data over 2.5
decades. The MME gives the most-probable near-Jupiter solar wind conditions for
times within the tested epoch, outperforming the input models and returning
quantified estimates of uncertainty.
