Why the Shock-ICME Complex Structure is Important: Learning From the Early 2017 September CMEs

Abstract

In the early days of 2017 September, an exceptionally energetic solar active region AR12673 aroused great interest in the solar physics community. It produced four X class flares, more than 20 CMEs and an intense geomagnetic storm, for which the peak value of the Dst index reached up to -142nT at 2017 September 8 02:00 UT. In this work, we check the interplanetary and solar source of this intense geomagnetic storm. We find that this geomagnetic storm was mainly caused by a shock-ICME complex structure, which was formed by a shock driven by the 2017 September 6 CME propagating into a previous ICME which was the interplanetary counterpart of the 2017 September 4 CME. To better understand the role of this structure, we conduct the quantitative analysis about the enhancement of ICME's geoeffectiveness induced by the shock compression. The analysis shows that the shock compression enhanced the intensity of this geomagnetic storm by a factor of two. Without shock compression, there would be only a moderate geomagnetic storm with a peak Dst value of -79 nT. In addition, the analysis of the proton flux signature inside the shock-ICME complex structure shows that this structure also enhanced the solar energetic particles (SEPs) intensity by a factor of ~ 5. These findings illustrate that the shock-ICME complex structure is a very important factor in solar physics study and space weather forecast.

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Cited by in corpus (18)

• CME-CME Interactions as Sources of CME Geo-effectiveness: The Formation of the Complex Ejecta and Intense Geomagnetic Storm in Early September 2017
• Eruption of a multi-flux-rope system in solar active region 12673 leading to the two largest flares in Solar Cycle 24
• Spectral Analysis of the September 2017 Solar Energetic Particle Events
• Triggering mechanism and material transfer of a failed solar filament eruption
• Solar Eruptions, Forbush Decreases and Geomagnetic Disturbances from Outstanding Active Region 12673
• Observational Analysis on the Early Evolution of a CME Flux-rope: Pre-flare reconnection and Flux-rope's Footpoint Drift
• Development of a coronal mass ejection arrival time forecasting system using interplanetary scintillation observations
• Sun-as-a-star Analysis of H$\alpha$ Spectra of a Solar Flare Observed by SMART/SDDI: Time Evolution of Red Asymmetry and Line Broadening
• Rotation and interaction of the September 8 and 10, 2014 CMEs tested with EUHFORIA
• Formation of a Magnetic Flux Rope in the Early Emergence Phase of NOAA Active Region 12673
• Different contributions to space weather and space climate from different big solar active regions
• Evolution of the Non-potential Magnetic Field in the Solar Active Region 12673 Based on a Nonlinear Force-free Modeling
• The formation and decay of sunspot penumbra in Active Region NOAA 12673
• The magnetic field environment of active region 12673 that produced the energetic particle events of September 2017
• Radial Evolution of ICME-Associated Particle Acceleration Observed by Solar Orbiter and ACE
• Space weather: the solar perspective -- an update to Schwenn (2006)
• Rapid Evolution of Bald Patches in a Major Solar Eruption
• Earth-affecting Solar Transients: A Review of Progresses in Solar Cycle 24