Thesis Proposal: The Storm Time Response of the Ring Current to ICMEs and CIRs using Van Allen Probe Observations
Abstract: During geomagnetic storms, large scale changes in the inner magnetosphere impact the radiation belt variability. Ring current particles can affect the outer radiation belt by changing the global magnetic field and introducing a free energy source to drive wave activity. Using Van Allen Probes (VAP) observations of the inner magnetosphere during magnetic storms driven by interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs), we characterize and compare their impact on the storm time ring current development and on the potential for electromagnetic ion cyclotron (EMIC) wave generation. We have developed an empirical model in magnetic local time (MLT) and L-shell of the ring current pressure development during the different storm phases (prestorm, main phase, early recovery, and late recovery) and for different species (H+, He+, O+, e-). While the H+ pressure response shows a similar source/convection pattern for ICME and CIR storms, the O+ response is distinctly different. The O+ pressure response is significantly stronger for ICME storms and it peaks at lower L shells, compared to H+, indicating that the hardness of the energy spectrum of the source population (at ~6 Re nightside plasma sheet) is different between O+ and H+. Our empirical model results are compared to simulation results from the Comprehensive Inner Magnetosphere-Ionosphere Model (CIMI). In addition, using VAP plasma and field observations, a linear theory based proxy for EMIC wave generation is used to predict the development of wave activity during storm times for ICME and CIR storms. We observe a slightly higher dusk side probability for wave activity for CIR storms over ICME storms.