Observation and modeling of complex transient structure in heliosphere followed by geomagnetic storm on May 10-11, 2024

TL;DR

This study combines multi-stage observations and modeling to analyze the propagation of complex CME/ICME structures in the heliosphere, culminating in a major geomagnetic storm on May 10-11, 2024.

Contribution

It introduces a comprehensive method integrating LASCO, IPS, and in situ data with a cone model and DBM to simulate complex CME interactions in the heliosphere.

Findings

Modeled ICME density distribution matches IPS and ACE data.

Complex CME interactions can be effectively modeled with combined observational data.

The approach validates the use of cone and DBM models for complex CME propagation.

Abstract

Complex CME/ICME structures in the solar wind often arising in the heliosphere as a result of interaction between two or more CMEs are very important due to their enhanced geoefficiency, but their modeling is difficult due to lack of observational data outside the solar corona. The outstanding evidence of such complex structure occurred on May 10-11,2024, when the strongest geomagnetic storm was caused by a series of successive CMEs emerged from the same solar AR13664. The complex formed from the first 4 CMEs of the series triggered a drop of the Dst-index to -412nT. The aim of this study is to consider propagation of these ICMEs in the heliosphere using observations at three stages: at the starting point observed with the LASCO, in the middle heliosphere by the IPS method and in situ at the L1 point with the ACE. The IPS observations were carried out on May 9 and 10 with the BSA LPI, which enables to build in the scanning mode 2D map of scintillation index m2 associated with enhancements of the integrated over the LOS plasma density over a range of the heliocentric distances 0.4-0.8AU. Evolution of the ICMEs in the heliosphere was described using a cone model in the selfsimilar approximation and kinematics according to the DBM. The initial spatial distributions of density at the cone base were determined from the LASCO images of the CMEs at the heights of 20Rsun, and then were rescaled according to radial distances to the position corresponding to the time of the BSA observations. It was shown that the modeled distribution of the ICME complex LOS density N2 over heliocentric distance is consistent with distribution of m2. Some discrepancies may characterize variation of the density structure inside the complex due to CME interaction. The modeled mean volume density of the ICME plasma at the L1 position agreed with in situ ACE measurements, which validates the developed expansion model.