Abstract
AbstractUltra low frequency (ULF) waves play a crucial role in transporting and coupling energy within the magnetosphere. During geomagnetic storms, dayside magnetospheric ULF wave power is highly variable with strong enhancements that are dominated by elevated solar wind driving. However, the radial distribution of ULF wave power is complex ‐ controlled interdependently by external solar wind driving and the internal magnetospheric structuring. We conducted a statistical analysis of observed storm‐time ULF wave power from the Van Allen Probes spacecraft within 2012–2016. Focusing on the dayside (06 < magnetic local time ≤ 15), we observe large enhancements across 3 < L < 6 and a steep L dependence during the main phase. We consider how accounting for concurrent magnetopause and plasmapause locations may reduce statistical variability and improve parameterization of spatial trends over and above using the L value. Ordering storm time ULF wave power by L provides the weakest dependences from those considered, whereas ordering by distance from the magnetopause is more effective. We also explore dependences on local plasma density and find that spatially localized ULF wave power enhancements are confined within high density patches in the afternoon sector (likely plasmaspheric plumes). The results have critical implications for empirical models of ULF wave power and radial diffusion coefficients. We highlight the necessity of improved characterization of the highly distorted storm‐time cold plasma density distribution, in order to more accurately predict ULF wave power.
Highlights
The terrestrial magnetosphere is host to a wealth of electromagnetic fluctuations that communicate information and transfer energy across the magnetospheric system
The data set of compressional Ultra low frequency (ULF) wave power, P, is statistically analyzed to assess storm time variations and dependences on the magnetopause and plasmapause boundaries
Through a consideration of the magnetopause and plasmapause boundaries, we determine that a significant part of the ULF wave power enhancement can be accounted for by the compressed magnetopause during the storm main phase
Summary
The terrestrial magnetosphere is host to a wealth of electromagnetic fluctuations that communicate information and transfer energy across the magnetospheric system. Amongst the most interesting are those fluctuations occurring within the ultra low frequency (ULF) wave band with frequencies ranging from ∼1−10 mHz (Jacobs et al, 1964). ULF waves play a crucial role in wider magnetospheric dynamics, associated with radial transport of the hazardous radiation belt population and resonant interactions with non-equilibrium particle distributions (e.g., Elkington et al, 2003). Sources of ULF waves lie both internally and externally to the magnetosphere. External sources include Kelvin-Helmholtz instabilities at the magnetopause flanks
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
