Validation and 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 depend on understanding the heliospheric magnetic field structure, which is essential for determining magnetic connectivity to the Sun and for the transport of nonthermal particles from the Sun to Earth and beyond. The abundance of near-Sun observations from recent missions [e.g., the Parker Solar Probe (PSP) and Solar Orbiter (SolO)] offers us a unique opportunity to evaluate and validate data-driven magnetohydrodynamic (MHD) SW models. This study employs the MHD SW model developed by Tasnim et al. (2018) to predict SW ion density, temperature, radial and non-radial velocity, and magnetic field as functions of position between the Sun and Earth. Tasnim et al. (2018) model incorporates solar wind acceleration, intrinsic non-radial magnetic fields, non-radial velocity at the source surface or inner boundary, and conservation of angular momentum. The radial evolution of the solar wind and its MHD predictions are studied for the period from December 1 to December 28, 2022, by using data from STEREO, PSP, and SolO. Predictions of the radial evolution of magnetic fields and temperature based on STEREO observations are consistent with those from PSP and SolO. However, the observed density and radial velocity profiles are steeper than predicted between 0.18 AU and 2.5 AU. A potential explanation for the rapid acceleration and low density of the SW wind in this region is the slightly elevated latitude of the PSP during this interval. To further investigate, a subsequent period (September 1 to September 28, 2020) with nearly constant latitude is analysed. Predicted SW plasma and magnetic field components during this interval, which are derived from Wind spacecraft data at the inner boundary to 1 AU, show strong agreement with 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.