engleski

CME-CME Interactions as Sources of CME Helio-effectiveness

Coronal Mass Ejections (CMEs) are the main space weather drivers in the heliosphere. It is known that the capability of individual CMEs to drive strong disturbances at Earth (“geo-effectiveness”) and other locations (“helio-effectiveness”) primarily depends on their speed, density, and magnetic field at impact, and that CME-CME interactions can often dramatically amplify the geo-effectiveness of the individual CMEs involved. However, the actual quantification of this amplification has been rarely investigated, and previous studies have mostly focused on the near-Earth region, i.e. without considering its full space-time evolution as the CMEs propagate to 1 AU and beyond. Here, we present a study on the role of CME-CME interactions as sources of CME helio-effectiveness by performing numerical simulations with the EUHFORIA heliospheric model. As a case study, we consider a sequence of geo-effective CMEs observed in September 2017. We perform observation-based simulations of magnetised CMEs, and quantify the resulting helio-effectiveness amplification of individual CMEs as a function of the CME-CME interaction phase and of the location within the CME structure. We then explore the possibility of existence of a “helio-effectiveness amplification zone”, i.e. a characteristic heliocentric distance where CME-CME interactions have the highest probability to develop into highly helio-effective events.

coronal mass ejections, space weather

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