The role of solar wind dynamics in the control of magnetospheric ULF wave power
Dimitry Pokhotelov
MSSL, University College London, UK
I. J. Rae (MSSL, UCL, UK), K. R. Murphy (GSFC, NASA, USA), I. R. Mann (Univ. of Alberta, Canada), H. Hietala (Imperial College, UK), E. K. J. Kilpua (Univ. of Helsinki, Finland)
First principle radiation belt models require the parameterisation of plasma wave power as an input for the assessment and forecast of the Earth’s radiation environment as a function of external or internal driving. These statistical parameterisations are required to model wave-particle interactions across the entire spectrum from mHz to kHz including: ELF-VLF frequency plasma waves, radial diffusion due to storm-enhanced ULF Pc 4-5 waves, and coherent interactions with ULF Pc 4-5 standing waves. Statistical distributions of magnetospheric wave power are known to be strongly dependant on solar wind parameters, particularly in the ULF range. Traditionally, time-average solar wind conditions are used to characterise an interval of wave-driven activity. To determine whether the dynamic properties of the solar wind is a critical factor in the solar wind driving of magnetospheric ULF wave power, we statistically characterise the ULF wave powers in the outer radiation belts as a function of the average and dynamic characteristics of the solar wind. We find that solar wind variability is an important controlling factor of ULF wave power inside the magnetosphere, and in particular the variability of IMF vector is of key importance while the variability of other parameters (solar wind density, ion temperature and velocity) being relatively less important. We also analyse the ULF power at various stages of ICME-driven magnetic storms characterised by different levels of mean solar wind parameters and their variabilities. We discuss these results in terms of future input into the first principle radiation belt models.