Complex Coronal Mass Ejection Structures and Associated Geo-effectiveness

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The Sun is the ultimate driver of the physical properties of the entire Heliosphere, and can cause severe perturbations to the near-Earth space environment due to large-scale dynamic events taking place in the solar atmosphere, such as Coronal Mass Ejections (CMEs). Our society is becoming increasingly dependent on technological assets that can be directly damaged by these, so-called, space weather events. Consequently, predicting the occurrence and detailed nature of such events is of critical importance to minimizing their damage. The characteristics of CMEs that determine their impact at Earth can change drastically if the CMEs encounter other large-scale structures on their way through the interplanetary medium, such as other CMEs. Statistical studies indicate that interacting CMEs, creating so-called complex ejecta structures, are an important source for the most intense space weather events. This project aims to investigate a multitude of ways in which these interactions can happen and reveal the resulting complex ejecta characteristics and space weather impacts. In turn, this will contribute towards better understanding and predicting the formation of some of the largest geomagnetic storms.The project includes significant science education and public outreach components. The PI and other members of the proposal team are contributors to the online website www.solarstormwatch.com, a website for real-time prediction with citizen involvement. They will continue this engagement as part of this project, amongst other through the development of complementary materials for public dissemination, including 3-D visualizations and multimedia materials. Funding is also included for the participation of undergraduate students in the research project. The overarching goal of this project is to carry out an in-depth study of complex phenomena associated with multiple, interacting CMEs or CMEs interacting with other solar wind streams, focusing on the physics behind the observed effects, and their resulting geo-effective potential. This will be done through: (i) 3-D numerical simulations with a state-of-the-art MHD code of idealized situations, (ii) combined 3-D numerical simulations and data analysis of selected real studies, and, (iii) analysis of in-situ measurements. Specifically, the ability to generate white-light images and in situ measurements will enable the inclusion of observational effects in the study when analyzing complex events and the validation of the numerical findings by direct comparisons between simulations and observations. The investigation will address the following science questions: 1) What are the different manifestations of CME-CME interaction observed remotely and measured in-situ? and what is their origin? 2) How does the interaction of successive CMEs compress, accelerate, deflect and rotate the CMEs? 3) What are the similarities and differences between CME-CME interaction and CME-CIR interaction? 4) What makes complex ejecta and compound streams so geo-effective?