Connecting the dots: Multi-point observations for solar wind science and forecasting

Atmospheric science and forecasting, concerned with a volume ~10¹³ m³, is underpinned by an extensive observational network; point measurements at 10k land-based stations, 4k ships and buoys, and around 1k dedicated balloon launches and aircraft; remote sensing from hundreds of radars and 10 dedicated operational satellites providing independent “look directions” through the atmosphere. By comparison, the heliosphere is a vastly under-sampled system. In the ~10²⁸ m³ volume contained within Earth orbit, there has been a maximum of 5 simultaneous point measurements and remote sensing from (at most) 3 simultaneous vantage points. This makes it difficult to reliably interpret observations in terms of the 3-dimensional structure and extent of solar wind transients. Solar Orbiter, Parker Solar Probe, STEREO-A and L1 monitors (and a possible future L5 monitor), as well as more limited solar wind measurements from planetary/cometary missions, will shortly provide unprecedented observational coverage and thus a unique opportunity to better understand solar wind transients. Nevertheless, sampling will remain sparse and connecting point observations and interpreting remote sensing observations will remain ambiguous. Global models of the solar wind can aid greatly in this regard. This talk will summarise how observations and models can be best combined to exploit the strengths of both, and what we can learn about solar wind transients.