Density structure measured by both PSP and Solar Orbiter. Proton density measurements (a) and magnetic field magnitude (b), corrected by a factor (R/R₀)² and (R/R₀)^1.6, respectively, to take the expansion from PSP (blue) to Solar Orbiter (orange) into account. The quantities are plotted as functions of t for PSP and as functions of t − τ for Solar Orbiter over a 2 h time interval (with τ = 137.6 h as determined by several cross-correlation methods; see Sect. 4.2). An average over 20 s was applied to the data to better highlight the global behavior of the density structures.