engleski

A study of the role of CME-CME interactions on CME geo- effectiveness with EUHFORIA

Coronal Mass Ejections (CMEs) are the main source of strong space weather disturbances at Earth and other locations in the solar system. While their impact is largely determined by their dynamic pressure and magnetic field, interactions with other CMEs can significantly alter their individual characteristics and enhance their (geo-)effectiveness. As observations in the heliosphere are limited, investigating such phenomena via physics-based models is therefore crucial to advance our understanding of complex CME events, and to assess the prediction capabilities at various locations. Here we present a comprehensive study of the role of CME-CME interactions on their (geo-)effectiveness, by performing simulations of complex CME events with the EUHFORIA heliospheric solar wind and CME propagation model. As a case study, we consider a sequence of 6 CMEs observed during the unusually active week of 4- 10 September 2017. As their source region moved on the solar disk due to the rotation, CMEs were launched over a wide range of longitudes, interacting with each other while paving the way for the propagation of the following ones. CME signatures were observed at Mars and at Earth, where intense disturbances and space weather events were triggered by CME-CME interactions. Using input parameters derived from multi-spacecraft remote-sensing observations of CMEs and their source region, we perform global simulations of the event using the spheromak CME model in EUHFORIA, and we investigate how their interactions affected the evolution of single CME structures and the in-situ properties at Earth and Mars. Results from this case study are complemented by a parametric study of CME-CME interactions, performed by running a set of simulations varying the initial CME parameters (e.g. speed, waiting time, magnetic field properties, density…), with the aim of quantifying the effect of such changes on their propagation and interaction. Results will benchmark our current prediction capabilities in the case of complex CME events and provide insights on their large-scale evolution in the heliosphere.

coronal mass ejections, MHD simulations, space weather

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