GEM: Onset and Consequences of Reconnection in the Magnetotail

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This project addresses compelling questions that have been the subject of continuing debate and controversy regarding the triggers of severe space weather activity. The team will follow the evolution of the Earth's magnetotail from a stable configuration to the onset of explosive magnetic reconnection using a state-of-the-art 3D kinetic particle-in-cell (PIC) model that has been modified to run efficiently on petascale computers. Magnetic reconnection is, in effect, the breaking and reconnecting of magnetic field lines, which is accompanied by an explosive release of energy, and is critical to the development of "severe weather" in space. An important additional feature of the project is that the simulations will be continued in time to follow the evolution of the magnetotail after the explosive energy release. This enables investigation of a number of observed phenomena connected to the space storm development - some only recently appreciated. This project has a high potential for delivering transformative new knowledge. Gaining knowledge about the interactions between processes that occur on disparate spatial and temporal scales is a major challenge in understanding the development of extreme events ranging from severe space weather to tornadoes to volcanic eruptions to earthquakes. The objectives and methodology in this project are closely aligned with the focus of the NSF Prediction of and Resilience against Extreme Events (PREEVENTS) program, which is co-funding the work described above. The project will support the training of a postdoctoral student, contributing to the future scientific workforce. The results of this work will be of interest to a range of discipline areas in the broader scientific community because magnetic reconnection occurs in space, astrophysical, and laboratory plasmas. In the longer term, new knowledge about the triggers of explosive energy release during space storms will improve space weather prediction.Progress in understanding the explosive onset of magnetic reconnection and its causes is enabled through the restructuring of PIC models to take advantage of petascale computers. PIC models follow the paths of charged particles as they move through self-consistent electromagnetic fields computed at points within a fixed mesh. To reduce the extremely large number of particles that the computer must follow and make the calculation tractable, the simulation uses computational superparticles, each of which may represent millions of charged particles. The VPIC model used in this project is a state-of-the-art, high performance, 3D fully kinetic particle-in-cell model. It is one of the fastest, most optimized, and most capable PIC models in the world. Simulations using this code have exceeded 3 trillion particles and 15 billion cells on petascale computers. An important aspect is that the model is able to simulate the instabilities and dynamics in the micro-scale diffusion region where reconnection occurs, while at the same time viewing the coupling between the diffusion region and the magnetotail at the larger scales important in the global storm development.