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Abstract Switchbacks, defined as Alfvénic reversals in magnetic field polarity, can dissipate their magnetic energy with heliocentric distance. To further investigate this, two distinct solar wind parcels tracing back to a similar solar source region were examined during a radial alignment between Parker Solar Probe (@25.8RS) and Solar Orbiter (@152RS). The one caveat was that the two probes were located on opposite sides of the heliospheric current sheet during the alignment. The two parcels contained a multitude of switchbacks—the parcel closer to the Sun was characterized as a switchback patch (SBP), where background proton velocity (v_p) is comparable to the pristine solar wind (v_sw), while the parcel farther from the Sun showed characteristics attributable to a microstream (MS;v_p > v_sw). It was found that (1) MS contains, on average, 30% fewer switchbacks than SBP, and (2) dynamic and thermal pressures decreased by up to 20% across switchback boundaries in SBP and relatively unchanged in MS. Magnetic relaxation can explain the lower number of switchbacks in MS compared to SBP. Switchback relaxation inside SBP can, in turn, accelerate plasma inside SBP over time and heliocentric distance, thus resulting inv_p>v_swin MS. Therefore, it is hypothesized that magnetic relaxation of switchbacks may cause SBPs to evolve into MSs over time and heliocentric distance. 

Abstract The radial evolution of interplanetary coronal mass ejections (ICMEs) is dependent on their interaction with the ambient medium, which causes ICME erosion and affects their geoefficiency. Here, an ICME front boundary, which separates the confined ejecta from the mixed, interacted sheath–ejecta plasma upstream, is analyzed in a multipoint study examining the ICME at 1 au on 2020 April 20. A bifurcated current sheet, highly filamented currents, and a two-sided jet were observed at the boundary. The two-sided jet, which was recorded for the first time for a magnetic shear angle <40°, implies multiple (patchy) reconnection sites associated with the ICME erosion. The reconnection exhaust exhibited fine structure, including multistep magnetic field rotation and localized structures that were measured only by separate Cluster spacecraft with the mission inter-spacecraft separation of 0.4–1.6R_E. The mixed plasma upstream of the boundary with a precursor at 0.8 au lacked coherency at 1 au and exhibited substantial variations of southward magnetic fields over radial (transverse) distances of 41–237R_E(114R_E). This incoherence demonstrates the need for continuous (sub)second-resolution plasma and field measurements at multiple locations in the solar wind to adequately address the spatiotemporal structure of ICMEs and to produce accurate space weather predictions.