Distinct Source Regions for Slow Solar Wind Populations Differentiated by Residual Energy during Parker Solar Probe Encounter 7

Abstract The properties of solar wind are closely related to its source region in the solar atmosphere. Here, we investigate the variability of solar wind measured by Parker Solar Probe (PSP) during Encounter 7 (E7) and connect it to spatiotemporal changes in magnetic connectivity to multiple solar sources in the solar atmosphere. During E7, PSP sequentially detected fast solar wind (FSW), Alfvénic slow solar wind (ASSW), and magnetic-velocity alignment structures (MVAS; with high magnitude of the magnetic field and velocity correlation coefficient C vb and moderately negative normalized residual energy σ r ). ASSW and MVAS both have ∣ C vb ∣ ∼ 1 but differ in σ r . We trace back to the solar atmosphere by applying potential field source surface modeling and ballistic backmapping, and find that FSW, ASSW, and MVAS belong to three distinct regions. Combining these results with EUV observations from SDO/AIA and Hinode/EUV Imaging Spectrometer, we find that magnetic footpoints in the first region oscillate between the center and boundary of a coronal hole, corresponding to variable solar wind containing FSW and MVAS. In the second region, footpoints lie on the western side of NOAA active region (AR) 12796, evidenced by open field lines, enhanced EUV intensity on the AIA map, and blueshifted Doppler velocity, indicating that ASSW may originate from the AR. Footpoints in the third region are primarily located in a quiet Sun region, a possible MVAS source region. These findings highlight the complex and dynamic linkage between solar wind variability and its diverse source regions.