Panel a: Hα line-core image and Doppler velocity maps (panel b) at 17:22:08 UT, panel c: at 17:42:17 UT, and panel d: at 17:52:32 UT. All velocity maps are clipped between ±7.5 km s⁻¹, i.e., the saturated white regions denote velocities exceeding this limit. The points p₁–p₄ refer to regions, which we examine in detail. The black contours show the regions with two spectral components indicating very strong redshifts. The labels α, β, and γ indicate three individual arch filaments, which are discussed in the text. Panel e: map of the uncertainties u_v of the LOS velocities from the line-core fits exemplary for the LOS map at 17:52:32 UT