Interpretation of the corotation effect of polar conic current sheets and their source at the Sun

In the epochs of the solar activity minima, the high-latitude heliosphere is dominated by the flow of fast solar wind proceeding from polar coronal holes. Polar conic current sheets (CCS) can form within this flow as cone-shaped surfaces bounded by large-scale current sheets. These conic current sheets extend from the source in a polar coronal hole to distances of several astronomical units from the Sun, where they were detected using the Ulysses data for 1994 and 2007. One of unresolved issues is the observed effect of partial corotation of the conic current sheets and the Sun, whereby the axis of symmetry of the conic current sheets rotates around the solar rotation axis at a frequency close to the Carrington rotation rate. In this paper, we propose a three-dimensional kinematic non-stationary model of plasma propagation in the region of the conic current sheets. The model explains the effect of partial corotation as a result of the superposition of radial solar wind streams from a non-uniform source that rotates synchronously with the Sun. Based on the analysis of Ulysses data and the new model, we show that the motion of the conic current sheets as a whole differs from the motion of plasma within them, and both have a collective nature. As the conic current sheets rotate, they form spiral-wound cones. This explains the observation of conic current sheets at different heliolatitudes.