Modeling ring current enhancements during magnetic storms

In order to develop predictive space weather models, the factors that lead to the development of large geomagnetic storms must first be understood. Changes in the solar wind can affect the Earth's magnetosphere and result in ring current enhancements, which are the primary driver of geomagnetic storms. During storms, induced electric and magnetic fields within the magnetosphere lead to the build up of energetic particles within the ring current and radiation belts. Such intense enhancements of the storm-time ring current result in decreases in Earth's surface magnetic field and in Dst. In order to explore the mechanisms responsible for the acceleration and injection of plasma sheet ions into the inner magnetosphere, we use single-particle tracking with time-dependent global magnetic and electric fields to model two different geomagnetic storms. We examine the contribution from various ionospheric source regions to the storm-time ring current, looking specifically at the role that IMF Bz plays in the development of storms and the mechanisms and features that result in the energization and injection of particles into the ring current. Results show that the energization and trapping of ionospheric H+ and O+ are highly dependent on solar wind conditions, and small scale structures in the current sheet are correlated with particle convection and energization. We also address differences observed between acceleration and injection mechanisms during substorms verses storms. Gaining a better understanding of the factors that are important in the development of geomagnetic storms and substorms will ultimately allow for the advance of predictive space weather models.