A Strategy to Close Key Questions about the Middle Solar Corona During this Decade

The middle corona, the region roughly spanning heliocentric altitudes from 1.5-6 R ⊙ , encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere.Eruptions that could disrupt the near-Earth environment propagate through it.Importantly, it also modulates inflow from above that can drive dynamic changes at lower heights in the inner corona.Consequently, this region is essential for comprehensively connecting the inner corona to the heliosphere and for developing corresponding global models.Nonetheless, because it is challenging to observe, the middle corona has been poorly studied by any solar remote sensing missions or instruments, extending back to the Solar and Heliospheric Observatory (SoHO) era.Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased.This paper summarizes the modern definition of the middle corona and key questions about it, and presents strategic recommendations to conquer the unsolved physics of the region based on integrated, multi-modality observational campaigns including:• prioritizing coordinated, comprehensive middle corona imaging and spectroscopy,• prioritizing radio facilities with middle corona capabilities,• prioritizing multi-perspective and coronal magnetic field measurements, and• improving data assimilation capabilities to integrate new, multi-perspective observations into data-driven coronal models.