In the realm of energy and space science, understanding the behavior of solar wind and its interactions with the Earth’s magnetosphere is crucial for predicting space weather events that can impact power grids and satellite communications. Researchers Sebastián Saldivia, Felipe Asenjo, and Pablo S. Moya from the Universidad de Chile have delved into the dispersive properties of magnetohydrodynamic (MHD) waves in the expanding solar wind, providing insights that could enhance our predictive capabilities and potentially inform energy sector strategies for mitigating space weather risks.
The team’s work, published in the journal “The Astrophysical Journal,” focuses on the effects of solar wind expansion on the dispersive properties of MHD waves. Using the Expanding Box Model (EBM), they examined the three normal modes of ideal MHD under a background magnetic field that follows the Parker spiral geometry. This geometry is a well-accepted model describing the shape of the solar magnetic field as it extends into the solar wind.
The researchers constructed the dispersion tensor from the linearized MHD-EBM equations and derived analytical expressions for the eigenfrequencies, magnetic compressibility, and the ratio of the parallel electric field to the perpendicular magnetic field of the magnetosonic modes. Their findings reveal that magnetic compressibility increases with heliocentric distance, aligning better with in-situ observations when expansion is included in the MHD-EBM framework. This trend shows a well-defined minimum at small radii and then increases linearly with distance, naturally reproducing the observed transition from Alfvénic to compressive fluctuations between approximately 0.3 and 1 astronomical units (AU).
The ratio of the parallel electric field to the perpendicular magnetic field reveals contrasting behaviors for the fast and slow modes. While the fast mode becomes more electrostatic with increasing distance, the slow mode evolves to a more magnetically dominated character. Expansion reduces the growth of their electromagnetic/compressive balance at large radii. These results demonstrate that solar wind expansion actively redistributes energy between magnetically compressive modes and purely transverse fluctuations with respect to the background magnetic field, playing a significant role in shaping the radial evolution of wave dynamics throughout the inner heliosphere.
For the energy sector, understanding these dynamics is vital for improving space weather forecasting models. Accurate predictions of solar wind behavior can help utilities and satellite operators implement protective measures to safeguard infrastructure against geomagnetic storms. By incorporating these findings into predictive models, the energy industry can better prepare for and mitigate the impacts of space weather events, ensuring a more resilient and reliable energy supply.
This article is based on research available at arXiv.