Submitting Campus

Daytona Beach

Department

Physical Sciences

Document Type

Article

Publication/Presentation Date

6-28-2025

Abstract/Description

Large‐amplitude ultra‐low frequency (ULF) waves in Earth's ion foreshock play a crucial role in the dayside dynamics and solar wind‐magnetosphere coupling. This study uses global hybrid‐Vlasov simulation results from Vlasiator to investigate the detailed physical processes in the early growth phase of the foreshock ULF waves. Using both spatial and temporal information, the wave phase speed is determined and used to track a specific phase front as the wave evolves. The space‐time evolution of the foreshock waves and the backstreaming ions responsible for the wave growth is analyzed and presented in the wave frame for the first time. We employ a state‐of‐the‐art linear dispersion solver, LEOPARD, to solve the wave dispersion relations using the ion distributions and compare the theoretical predictions with the measured wave phase speed and growth rate. The measured phase speed in the spacecraft (or stationary) frame is unexpectedly high at the initial growth stage but later decreases to the predicted level and exhibits an increasing trend over time that aligns with theoretical expectations. The measured and predicted growth rates share the same decreasing trend over time, but the predicted values are consistently lower than the measured growth rate by ∼25%. The comparison suggests that the foreshock waves in the Vlasiator simulation are likely generated through the ion‐ion right‐hand resonant instability, but there are discrepancies with linear theory that are not explained yet and require further investigation.

Publication Title

Journal of Geophysical Research: Space Physics

DOI

https://doi.org/10.1029/2025JA033848

Publisher

John Wiley & Sons, Inc

Grant or Award Name

NASA Grants 80NSSC20K0801, 80NSSC24K0677, NSF GEM Grant 2420710, European Research Council Starting Grant 200141‐QuESpace, Consolidator Grant GA682068‐ PRESTISSIMO received by the Vlasiator PI. Vlasiator has also received funding from the Academy of Finland, Research Council of Finland Grants 361901 and 352846, Research Council of Finland (Grant 322544) and from the European Union (ERC Grant WAVESTORMS—101124500)

Additional Information

Dr. Zhang was not affiliated with Embry-Riddle Aeronautical University at the time this paper was published.

Download

Share

COinS