Speaker
Description
Coronal mass ejections (CMEs) with a strong and sustained southward magnetic field component are the main drivers of strong geomagnetic activity at Earth. One of the greatest challenges in space weather is accurately forecasting their arrival and magnetic structure, essential towards mitigating their impact to both space and ground systems. As CMEs propagate from the Sun, they undergo many processes that affect their evolution, including interactions with other solar wind transients which increase the complexity of their structure. Thus, their exact internal structure can only be known through direct in situ spacecraft measurements.
Using magnetic field observations taken by Solar Orbiter whilst it was located far upstream of the Earth at 0.4 AU, we present the first real-time predictions of the magnetic structure of two CME events at Earth, launched on the 17th and 23rd March 2024 respectively, and the resulting geomagnetic impact. Despite the large heliocentric distance between measurement at Solar Orbiter and CME arrival at Earth, predictions of the in situ magnetic structure at Earth were remarkably similar to what was later observed. Combining the predicted CME arrival time at Earth produced by the ELEvo model with the predicted magnetic structure as an input to the Temerin and Li model, values of the minute resolution Dst index were produced, with prediction lead times of 15.3 and 7.1 hours, respectively. Qualitatively, our predictions replicated the observed geomagnetic response profiles well, though underestimated storm intensity during already disturbed conditions.
We also retrospectively investigate the events and conditions surrounding their propagation, evaluating the effect on our predictions of the CME magnetic structure and the resulting geomagnetic impact. Our approach demonstrates how future real-time upstream monitors could advance our ability to forecast space weather impacts with actionable lead times, whilst also identifying their limitations.
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