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1. Slow solar wind modeling of the Metis/Solar Orbiter – Parker Solar Probe quadrature

   https://doi.org/10.1088/1742-6596/2544/1/012007  

   Adhikari, L; Zank, G P; Telloni, D; Zhao, L -L; Pitna, A (July 2023, Journal of Physics: Conference Series)

   Abstract In January 2021, Metis/SolO and PSP formed a quadrature from which the slow solar wind was able to be measured from the extended solar corona (3.5 – 6.3 R ⊙ ) to the very inner heliosphere (23.2 R ⊙ ). Metis/SolO remotely measured the coronal solar wind, finding a speed of 96 – 201 kms −1 , and PSP measured the solar wind in situ, finding a speed of 219.34 kms −1 . Similarly, the normalized cross-helicity and the normalized residual energy measured by PSP are 0.96 and -0.07. In this manuscript, we study the evolution of the proton entropy and the turbulence cascade rate of the outward Elsässer energy during this quadrature. We also study the relationship between solar wind speed, density and temperature, and their relationship with the turbulence energy, the turbulence cascade rate, and the solar wind proton entropy. We compare the theoretical results with the observed results measured by Metis/SolO and PSP. 

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2. An Empirically Driven MHD Model to Predict the Solar Wind at Parker Solar Probe and Solar Orbiter during the Current Solar Minimum

   Kim, T. K.; Pogorelov, N.; Arge, C. N.; Jones-Mecholsky, S. I. (December 2020, American Geophysical Union, Fall Meeting 2020, abstract #SH021-08)

   null (Ed.)

   Since the launch on 2018 August 12, the Parker Solar Probe (PSP) has completed its first five orbits around the Sun, having reached down to ~28 solar radii at perihelion 5 on 2020 June 7. More recently, the Solar Orbiter (SolO) made its first close approach to the Sun at 0.52 AU on 2020 June 15, nearly 4 months after the launch. Using a 3D heliospheric MHD model coupled with the Wang-Sheeley-Arge (WSA) coronal model using the Air Force Data Assimilative Photospheric flux Transport (ADAPT) magnetic maps as input, we simulate the time-varying inner heliosphere, including the trajectories of PSP and SolO, during the current solar minimum period between 2018 and 2020. Above the ADAPT-WSA model outer boundary at 21.5 solar radii, we solve the Reynolds averaged MHD equations with turbulence and pickup ions taken into account and compare the simulation results with the PSP solar wind and magnetic field data, with particular emphasis on the large-scale solar wind structure and magnetic connectivity during each solar encounter. 

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3. 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.)
4. Characterization of the Alfvén Transition in the Young Solar Wind using Parker Solar Probe Observations Approaching Solar Maximum

   https://doi.org/10.3847/1538-4357/ae2c78  

   Adhikari, Subash; Bandyopadhyay, Riddhi; Goodwill, Joshua; Matthaeus, William H; Ruffolo, David; Thepthong, Panisara; Pongkitiwanichakul, Peera; Roy, Sohom; Pecora, Francesco; Chhiber, Rohit; et al (January 2026, The Astrophysical Journal)

   Abstract Close to Earth, the solar wind is usually super-Alfvénic, i.e., the speed of the solar wind is much larger than the Alfvén speed. However, in the lower coronal regions, the solar wind is mostly sub-Alfvénic. With the Parker Solar Probe (PSP) crossing the boundary between the sub- and super-Alfvénic flow, R. Bandyopadhyay et al. performed a turbulence characterization of the sub-Alfvénic solar wind with initial data from encounters 8 and 9. In this study, we reexamine the turbulence properties such as turbulence amplitude, anisotropy of the magnetic field variance, intermittency, and switchback strength using PSP data from encounters 8–19. The later orbits probe lower altitudes and experience sub-Alfvénic conditions more frequently, providing a greater statistical coverage to contrast sub- and super-Alfvénic solar wind. These later orbits also extend the observations from near solar minimum at launch to near solar maximum conditions. Also, by isolating the intervals where the solar wind speed is approximately equal to the Alfvén speed, we explore the transition in more detail. We show that the amplitude of the normalized magnetic field fluctuation is smaller for the sub-Alfvénic samples. While solar wind turbulence in general is shown to be anisotropic, the sub-Alfvénic samples are more anisotropic than the super-Alfvénic samples, in general. Further, we show that the sub- and super-Alfvénic samples do not show much distinction in terms of intermittency strength. Finally, consistent with prior results, we find no evidence for polarity reversing >90° switchbacks in the sub-Alfvénic solar wind. 

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5. Modeling the Solar Wind during Different Phases of the Last Solar Cycle

   https://doi.org/10.3847/2041-8213/acc5ef  

   Huang, Zhenguang; Tóth, Gábor; Sachdeva, Nishtha; Zhao, Lulu; van der Holst, Bart; Sokolov, Igor; Manchester, Ward B.; Gombosi, Tamas I. (April 2023, The Astrophysical Journal Letters)

   Abstract We describe our first attempt to systematically simulate the solar wind during different phases of the last solar cycle with the Alfvén Wave Solar atmosphere Model (AWSoM) developed at the University of Michigan. Key to this study is the determination of the optimal values of one of the most important input parameters of the model, the Poynting flux parameter, which prescribes the energy flux passing through the chromospheric boundary of the model in the form of Alfvén wave turbulence. It is found that the optimal value of the Poynting flux parameter is correlated with the area of the open magnetic field regions with the Spearman’s correlation coefficient of 0.96 and anticorrelated with the average unsigned radial component of the magnetic field with the Spearman’s correlation coefficient of −0.91. Moreover, the Poynting flux in the open field regions is approximately constant in the last solar cycle, which needs to be validated with observations and can shed light on how Alfvén wave turbulence accelerates the solar wind during different phases of the solar cycle. Our results can also be used to set the Poynting flux parameter for real-time solar wind simulations with AWSoM. 

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