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1. Dark Solar Wind

   https://doi.org/10.1103/PhysRevLett.129.211101  

   Chang, Jae Hyeok; Kaplan, David E.; Rajendran, Surjeet; Ramani, Harikrishnan; Tanin, Erwin H. (November 2022, Physical Review Letters)
2. The near-Sun streamer belt solar wind: turbulence and solar wind acceleration

   https://doi.org/10.1051/0004-6361/202039872  

   Chen, C. H.; Chandran, B. D.; Woodham, L. D.; Jones, S. I.; Perez, J. C.; Bourouaine, S.; Bowen, T. A.; Klein, K. G.; Moncuquet, M.; Kasper, J. C.; et al (June 2021, Astronomy & Astrophysics)

   The fourth orbit of Parker Solar Probe (PSP) reached heliocentric distances down to 27.9 R ⊙ , allowing solar wind turbulence and acceleration mechanisms to be studied in situ closer to the Sun than previously possible. The turbulence properties were found to be significantly different in the inbound and outbound portions of PSP’s fourth solar encounter, which was likely due to the proximity to the heliospheric current sheet (HCS) in the outbound period. Near the HCS, in the streamer belt wind, the turbulence was found to have lower amplitudes, higher magnetic compressibility, a steeper magnetic field spectrum (with a spectral index close to –5/3 rather than –3/2), a lower Alfvénicity, and a ‘1∕ f ’ break at much lower frequencies. These are also features of slow wind at 1 au, suggesting the near-Sun streamer belt wind to be the prototypical slow solar wind. The transition in properties occurs at a predicted angular distance of ≈4° from the HCS, suggesting ≈8° as the full-width of the streamer belt wind at these distances. While the majority of the Alfvénic turbulence energy fluxes measured by PSP are consistent with those required for reflection-driven turbulence models of solar wind acceleration, the fluxes in the streamer belt are significantly lower than the model predictions, suggesting that additional mechanisms are necessary to explain the acceleration of the streamer belt solar wind. 

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3. Solar Spicules, Filigrees, and Solar Wind Switchbacks

   https://doi.org/10.3847/1538-4357/ad23e0  

   Lee, Jeongwoo; Wang, Haimin; Wang, Jiasheng; Wang, Meiqi (March 2024, The Astrophysical Journal)

   Abstract Spicules, the smallest observable jetlike dynamic features ubiquitous in the chromosphere, are supposedly an important potential source for small-scale solar wind transients, with supporting evidence yet needed. We studied the high-resolution Hαimages (0.″10) and magnetograms (0.″29) from the Big Bear Solar Observatory to find that spicules are an ideal candidate for the solar wind magnetic switchbacks detected by the Parker Solar Probe (PSP). It is not that spicules are a miniature of coronal jets, but that they have unique properties not found in other solar candidates in explaining solar origin of switchbacks. (1) The spicules under this study originate from filigrees, all in a single magnetic polarity. Since filigrees are known as footpoints of open fields, the spicule guiding field lines can form a unipolar funnel, which is needed to create an SB patch, a group of field lines that switch from one common base polarity to the other polarity. (2) The spicules come in a cluster lined up along a supergranulation boundary, and the simulated waiting times from their spatial intervals exhibit a number distribution continuously decreasing from a few seconds to ∼30 minutes, similar to that of switchbacks. (3) From a time–distance map for spicules, we estimate their occurrence rate as 0.55 spicules Mm⁻²s⁻¹, which is sufficiently high for detection by PSP. In addition, the dissimilarity of spicules with coronal jets, including the absence of base brightening and low correlation with EUV emission, is briefly discussed. 

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4. Solar Wind Temperature Isotropy

   https://doi.org/10.1103/PhysRevLett.123.145101  

   Yoon, P. H.; Seough, J.; Salem, C. S.; Klein, K. G. (October 2019, Physical Review Letters)
5. Solar Wind Simulations along the Parker Solar Probe Trajectory

   Hegde, D. V. (December 2021, AGU Fall Meeting 2021, held in New Orleans, LA, 13-17 December 2021, id. SH55C-1858.)