Heliospheric current sheet and fast solar wind as modeled by EUHFORIA. Top panel: modeled fast solar wind and HCS in 3D presentation together with STEREO-A, STEREO-B, and Earth. The colorful sphere in the middle of the domain shows the solar wind velocities at the inner boundary of EUHFORIA (at a distance of 0.1 AU) while the colorful isosurfaces depict velocities between 580–648 km s⁻¹. The HCS is represented by the gray shaded surface. Bottom panel: corresponding magnetic field polarity map, with the HCS at the border of positive (red) and negative (blue) polarity and marked positions of the AR12734 and Earth.