Unexpected Behavior of the Solar Wind Mass Flux During Solar Maxima: Two Peaks at Middle Heliolatitudes

Abstract

In this work we study the temporal and latitudinal variations of the solar wind mass flux at 1 AU derived from SOHO/SWAN data on backscattered solar Lyman- $\alpha $ radiation in 1996 – 2018. Previously Katushkina et al. (J. Geophys. Res. 118, 2800, 2013) have shown that the latitudinal profiles of the solar wind mass flux during the solar maximum 2001 – 2003 have two separate peaks at middle heliolatitudes. In this work we provide the data for the last solar maximum in 2014 – 2016 and show that the specific latitudinal distribution appears again. However, in 2014 – 2016 the two peaks are less separated and sometimes merged to one peak. For several years we have performed a comparison of SWAN observations with the results of the WSA-Enlil model, which is a coupled 3D time-dependent model of the solar wind propagation from the solar corona to the heliosphere. It is shown that the WSA-Enlil model confirms qualitatively the latitudinal distribution of the solar wind found from the SWAN data, although there are some quantitative differences. Physical reasons for the formation of this latitudinal structure at the solar maxima are discussed. Further investigation is needed and could provide new links between the solar corona and the heliospheric environment.