If directed toward Earth, they can cause significant space weather effects upon impact with the near-Earth environment. They conclude that knowledge of the CME magnetic structure at the Sun is an important factor in space weather forecasting, but the CME evolution after eruption has to be taken into account in order to improve current predictions.Ĭoronal mass ejections (CMEs) are large clouds of plasma and magnetic flux expelled from the Sun into the heliosphere. They find that 65% of the events change their orientations by less than 90°. They also estimate the orientations of the CME axes at the Sun and at Earth. They report that the magnetic structures match closely only in 20% of the events studied. They use observations of the solar disc to determine the magnetic structure at the Sun and then compare it with the magnetic structure estimated via magnetic field measurements near Earth. (2018) study 20 CMEs observed both at the Sun and at Earth. Predicting the magnetic structure well before CME arrival at Earth is one of the major goals in space weather forecasting. The ability of a CME to drive a geomagnetic storm is given largely by how its magnetic field is configured. Key PointsĬoronal mass ejections (CMEs) are huge eruptions from the Sun that can cause myriad of space weather effects at Earth. Moreover, we emphasize that determination of the intrinsic flux rope type is a crucial input for CME forecasting models. While occasionally the intrinsic flux rope type is a good proxy for the magnetic structure impacting Earth, our study highlights the importance of capturing the CME evolution for space weather forecasting purposes. For the majority of the cases, the rotation is several tens of degrees, while 35% of the events change by more than 90°. We also determine the change in the flux rope tilt angle between the Sun and Earth. The percentage rises to 55% when intermediate cases (where the orientation at the Sun and/or in situ is close to 45°) are considered as a match. We find that only 20% of the events studied match strictly between the intrinsic and in situ flux rope types. Our study shows that the intrinsic flux rope type can be estimated for CMEs originating from different source regions using a combination of indirect proxies.
In this article, we compare the intrinsic flux rope type, that is, the CME orientation and handedness during eruption, with the in situ flux rope type for 20 CME events that have been uniquely linked from Sun to Earth through heliospheric imaging. Predicting the magnetic field within an Earth-directed coronal mass ejection (CME) well before its arrival at Earth is one of the most important issues in space weather research.
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