Reconstructed Evolution of Latitudinal Profiles of the Solar Wind during the Past 60 yr

The latitudinal structure of the solar wind varies with the solar activity, and the knowledge of its history is needed to understand the interaction of the heliosphere with the local interstellar medium and construction of realistic models of the heliosphere, with observation-verifiable predictions. The solar wind structure at 1 au is researched from the ecliptic plane using remote-sensing methods, mostly interplanetary scintillations, but available data reach only to 1985. In this paper, we extend the history of the evolution of the latitudinal profiles of the solar wind to the beginning of in situ solar wind observations in 1964. To that end, we define a set of proxies subjected to principal component analysis suitable to reproduce the actually observed evolution and available back to 1964. To reconstruct the density, we need to reconstruct the alpha content during the interval 1964–1974. We develop the alpha reconstruction method and are now able to reconstruct the evolution of the solar wind for both speed and density for the interval 1964–2026. The WawHelioIon MP model thus obtained is the zeroth model for an extension further in time, to be performed based on helioglow lightcurves from a new experiment, GLOWS, on board a new NASA mission, IMAP.