Internal Structure of the Magnetic Funnel in the Polar Heliosphere

Abstract

According to data obtained by the Ulysses spacecraft in 2017, high-latitude current sheets have been discovered in the polar heliosphere. They have been observed during solar activity minima in 1994 and 2007 at a distance of 2–3 AU above the south pole of the Sun. The discovered current sheets formed a conical surface rotating as a whole around the Sun's rotation axis with the Carrington period. In this study, a semianalytical MHD model of conical current sheets is developed. The internal structure of heliospheric region bounded by these sheets—a magnetic funnel with reduced solar wind speed and the plasma beta—has been studied. Solutions corresponding to different intersections of the funnel by the Ulysses spacecraft have been obtained under different conditions near the Sun. The conditions under which the dimensions of the funnel agree with observations are clarified. For the first time, situations are treated in which the plasma and magnetic field parameters inside the funnel vary quasi-periodically in space. The study of the magnetic funnel structure challenges new issues for solar physics, whose solutions will enable a better understanding of the physical conditions on the early Earth and the features of the primary biosphere formation.