Parker Solar Probe - Solar Orbiter radial alignment study: evolution of the heliospheric current sheet

We present the study of a radial alignment between Parker Solar Probe and Solar Orbiter occurring at the end of April 2021. The two spacecraft were respectively at ~0.075 and ~0.9 au from the Sun. With the help of a propagation method, we identified the same density structure crossing both spacecraft, with a time delay of ~138 h between the two. This density structure is part of the heliospheric plasma sheet. We found that for this event, in-situ density measurements were concordant with radial gradients, while the magnetic field measurements were more concordant with longitudinal gradients. The structure is moreover inferred to have been generated by interchange reconnection in the high corona (2-3 solar radii), as observations are not in agreement with a generation by reconnection of the solar wind open field lines.