The heliospheric modulation of electrons and positrons over a complete solar cycle
2019 July 22
The solutions of a comprehensive three-dimensional drift model are compared to $PAMELA$ and $AMS$-02 spectra of electrons and positrons in order to describe and understand their different modulation down to 1 MeV. This is based on newly constructed very local interstellar spectra. The focus of the study is on a full solar cycle, the period from 2006 to 2017. Comparison of observations and modeling provides insight into how the three major diffusion coefficients change during a complete solar cycle, especially during a prolonged solar minimum and the period of the polarity reversal of the magnetic field during solar maximum activity, and to what extent drift effects evolve. In this context, the electron to positron ratio is computed from 1 MeV to 50 GeV, explaining the $PAMELA$ and $AMS$-02 observed ratio in detail. Predictions are made of what may be observed during the next, imminent solar minimum.