Microphysical Diversity in Two Very Closely Spaced Magnetic Switchbacks Observed by Parker Solar Probe

Abstract

Parker Solar Probe observations near the Sun reveal frequent, sudden reversals of the magnetic field known as switchbacks (SBs). Despite their ubiquity, the internal plasma structure and associated heating within SBs remain poorly understood. We present a case study of two closely spaced SBs (referred in text as SB_1 and SB_2) observed on 24 January 2020 using high-cadence magnetic and plasma measurements. Magnetic fluctuations are decomposed into components parallel and perpendicular to the mean field, and their power spectra are analyzed to characterize the turbulent cascade. The Partial Variance of Increments (PVI) method is applied to identify intermittent current-sheet-like features. Both SB intervals exhibit clear Alfvenic behavior and enhanced radial flow; however, their microphysics differ: SB_1 shows a higher proton temperature, larger fluctuation amplitudes, and a denser population of current sheets compared to SB_2. The two events also differ in spectral index, with SB_1 exhibiting a steeper perpendicular slope than SB_2. The elevated intermittency, proton temperature, and transient $β> 1$ excursion in SB_1 suggest that localized dissipation at small-scale structures is a plausible driver of the observed heating. These findings demonstrate that SBs are not uniform kinematic deflections but dynamically evolving plasma structures whose internal turbulence may regulate local energy conversion and contribute to the spatially intermittent heating of the near-Sun solar wind.