Linking remote imagery of a coronal mass ejection to its in situ signatures at 1 AU

TL;DR

This study demonstrates how remote white-light imaging of a coronal mass ejection (CME) can predict its internal structure and trajectory at 1 AU, aiding space weather forecasting.

Contribution

It shows the first successful link between remote CME observations and in situ signatures at 1 AU, including structure and direction predictions.

Findings

CME connected to in situ ICME with a 45-degree axis inclination

Remote imaging tracks CME from Sun to 1 AU

CME morphology relates to in situ three-part structure

Abstract

In a case study (June 6-7, 2008) we report on how the internal structure of a coronal mass ejection (CME) at 1 AU can be anticipated from remote observations of white-light images of the heliosphere. Favorable circumstances are the absence of fast equatorial solar wind streams and a low CME velocity which allow us to relate the imaging and in-situ data in a straightforward way. The STEREO-B spacecraft encountered typical signatures of a magnetic flux rope inside an interplanetary CME (ICME) whose axis was inclined at 45 degree to the solar equatorial plane. Various CME direction-finding techniques yield consistent results to within 15 degree. Further, remote images from STEREO-A show that (1) the CME is unambiguously connected to the ICME and can be tracked all the way to 1 AU, (2) the particular arc-like morphology of the CME points to an inclined axis, and (3) the three-part structure of the CME may be plausibly related to the in situ data. This is a first step in predicting both the direction of travel and the internal structure of CMEs from complete remote observations between the Sun and 1 AU, which is one of the main requirements for forecasting the geo-effectiveness of CMEs.