Bibliography
Notice:

ULF Wave Driven Radial Diffusion During Geomagnetic Storms: A statistical analysis of Van Allen Probes observations
Author  Sandhu, J.; Rae, I.; Wygant, J.; Breneman, A.; Tian, S.; Watt, C.; Horne, R.; Ozeke, L.; Georgiou, M.; Walach, M.T.; 
Keywords  ULF waves; radial diffusion; outer radiation belt; Van Allen Probes; Geomagnetic storms 
Abstract  Abstract The impact of radial diffusion in storm time radiation belt dynamics is welldebated. In this study we quantify the changes and variability in radial diffusion coefficients during geomagnetic storms. A statistical analysis of Van Allen Probes data (2012 − 2019) is conducted to obtain measurements of the magnetic and electric power spectral densities for Ultra Low Frequency (ULF) waves, and corresponding radial diffusion coefficients. The results show global wave power enhancements occur during the storm main phase, and continue into the recovery phase. Local time asymmetries show sources of wave power are both external solar wind driving and internal sources from coupling with ring current ions and substorms. Wave power enhancements are also observed at low L values (L < 4). The accessibility of wave power to low L is attributed to a depression of the Alfvén continuum. The increased wave power drives enhancements in both the magnetic and electric field diffusion coefficients by more than an order of magnitude. Significant variability in diffusion coefficients is observed, with values ranging over several orders of magnitude. A comparison to the Kp parameterised empirical model of Ozeke et al. (2014) is conducted and indicates important differences during storm times. Although the electric field diffusion coefficient is relatively well described by the empirical model, the magnetic field diffusion coefficient is approximately ∼ 10 times larger than predicted. We discuss how differences could be attributed to dataset limitations and assumptions. Alternative stormtime radial diffusion coefficients are provided as a function of L* and storm phase. 
Year of Publication  2021 
Journal  Journal of Geophysical Research: Space Physics 
Volume  n/a 
Number of Pages  e2020JA029024 
Section  
Date Published  03/2021 
ISBN  
URL  https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JA029024 
DOI  https://doi.org/10.1029/2020JA029024 