Merged Interplanetary Data From L1: MIDL

Abstract

The availability and accuracy of upstream solar wind conditions are critical for solar wind—magnetosphere coupling studies, whether based on observations or numerical models and simulations. We present the Merged Interplanetary Data from L1 (MIDL), which merges 1‐min magnetic field and plasma observations from ACE, DSCOVR, and Wind through a three‐stage algorithm: per‐satellite filtering and despiking, multi‐satellite quality screening with agreement‐first source selection, and using the median of the selected sources for each variable group. Special care is taken to minimize sudden changes in the data when sources change. The merged data can be propagated to a user set distance from Earth including Moon's orbit. MIDL provides two propagation methods: the traditional ballistic approach with proper handling of shocks and one‐dimensional magnetohydrodynamic simulation. Comparison with OMNI over 2005–2025 shows good agreement (Pearson for , 0.96 for density, 0.86 for ) with no systematic bias. MIDL achieves near‐complete coverage (%) for the magnetic field and coverage exceeding 95% for the plasma parameters for all years, compared to OMNI's % and %, respectively. The multi‐satellite consensus reduces vulnerability to data gaps, instrumental artifacts, and propagation errors. The data set is publicly available through a web interface https://csem.engin.umich.edu/MIDL and also through a public Python package CSEM‐MIDL. MIDL is well‐suited for use as simulation boundary conditions and for statistical solar wind studies.