Assessment of the generalized equatorial model for the accelerating solar wind using Multi Spacecraft Observations

Kurzfassung

Studies of the solar wind (SW) and its sources rely on understanding the structure and arrangement of the heliospheric magnetic field, which is significant for understanding how magnetic field lines connect to the Sun and for the transport of nonthermal particles from the Sun to Earth and beyond. The present-day abundance of observations near the Sun, e.g., from Parker Solar Probe (PSP) and Solar Orbiter (SolO), provides a novel opportunity to assess and improve MHD SW models. In this study, we predict the SW ion density, temperature, radial and non-radial velocity, and magnetic field as a function of position between the Sun and the Earth using Tasnim et al. (2018) 's magnetohydrodynamic (MHD) SW model. Tasnim et al. (2018) includes the effects of solar wind acceleration, non-radial intrinsic magnetic fields, and flows at the source surface/inner boundary, and conservation of angular momentum. We investigate the radial evolution of the solar wind and its MHD predictions during the period December 1 to December 28, 2022, using STEREO, PSP, and SolO. The predictions of the radial evolution of magnetic fields and temperature based on STEREO observations agree well with those from PSP and SolO. However, results show that the density and radial velocity profiles are steeper than our predictions between 0.18 AU and 2.5 AU. One possible reason for the rapid acceleration and low density of the SW wind between 0.18 AU and 2.5 AU is that the PSP's latitude was slightly higher than the rest of the period. We then select another period (1 September to 28 September 2020), in which the latitude remains nearly constant, and find that the predicted SW plasma and magnetic field components, using Wind spacecraft data from the inner boundary to 1 AU, show good agreement with the corresponding PSP observations at increasing heliocentric distances. Agreement between predictions and observations underscores the importance of incorporating intrinsic non-radial velocity and magnetic field effects from the inner boundary, extending beyond 1 astronomical unit (AU), while upholding the crucial principle of angular momentum conservation.