Authors: Lidiya Ahmed; Michael Stevens; Samuel Badman; Aileen Niesta

Most solar-wind prediction methods rely on boundary conditions specified at a fixed inner radius, typically derived from coronal models. While these approaches are powerful, they are computationally expensive and lack direct observational validation at the boundary itself. Recent work has explored reconstructing inner-boundary conditions directly from in situ measurements by mapping observations back to the Sun using ballistic mapping. However, such back-propagation approaches must account for solar-wind evolution between the observation point and the inner boundary, including solar wind acceleration and stream interactions. NASA’s Parker Solar Probe provides a great opportunity for upstream monitoring by sampling the solar wind much closer to the Sun, providing observations of plasma that may later propagate toward Earth. In particular, during its cruise phase (R > 0.25 AU), Parker can remain approximately Parker-spiral aligned with Earth for extended periods.

In this study, we explore a HUX (Heliospheric Upwind eXtrapolation) like approach, in which Parker measurements are inserted at intermediate heliocentric distances and propagated out to 1 AU. We implement a simplified heliospheric model to solve the Inviscid Burger’s equation that captures the interaction of fast and slow streams(unlike ballistic mapping) while remaining computationally efficient. 

We apply this framework to Parker Solar Probe observations and compare the resulting solar-wind structure and predictions at 1 AU with in-situ measurements and those obtained from boundary-driven simulations. By examining the role of spacecraft position, longitudinal alignment, and radial distance, we assess when intermediate-distance measurements provide meaningful improvements over traditional approaches. This work builds toward a data-driven heliospheric modeling strategy and serves as a test of how near-Sun, in situ observations can be used as upstream monitors to improve solar wind forecasting.