ISTPNext and the ITM Great Observatory: The need for international coordination in Heliophysics

Heliophysics is the study of the Sun and its effects throughout the solar system. It covers an incredible range of scales, from plasma physics at the electron scale to the boundary that separates our solar system from interstellar space. It also includes a diverse array of sub disciplines and expertise, with measurements spanning in situ particles and fields from the ionosphere out to the Sun’s corona, to remote sensing of the Sun, heliosphere, and near-Earth environment at multiple wavelengths and in energetic neutral atom observations. Many of the biggest unanswered science questions that remain across Heliophysics center around the interconnectivity of the different physical systems that comprise the Heliosphere, and the role of mesoscale dynamics in modulating, regulating, and controlling that interconnected behavior. These are complex, yet ultimately fundamental questions of how the Sun-Heliosphere and Geospace interact, and answers are needed to more accurately predict and model space weather impacts on and around Earth, the moon, and Mars. To answer these long-standing questions on the Sun-Heliosphere and Geospace as system-of-systems, we believe that Heliophysics requires a coordinated, deliberate, worldwide scientific effort. We suggest that the worldwide Heliophysics discipline should embark on a grand program to study these system-of-systems holistically, with coordinated, multipoint measurements, with particular emphasis on resolving mesoscale dynamics, and a whole-of-science approach that includes ground-based measurements and advanced numerical modeling. Without such a unified, next generation ISTP-type program, these questions will remain largely unanswered. In this paper we lay out the case for such an approach, and discuss how the ITM community is using the upcoming NASA GDC mission as a cornerstone to develop the ITM Great Observatory, a grass-roots, holistic approach modeled after ISTP to study the ITM system.