Identifying and Predicting Coronal Mass Ejection Occurrence: Observational Checklists for Space Weather Forecasters

Ejections of magnetized plasma from the Sun, known as coronal mass ejections, can drive major geomagnetic activity if Earth-directed, and are therefore monitored by space weather forecasters. The current focus being the forecast of the arrival time of a coronal mass ejection at Earth and the level of geomagnetic impact. Available instrumentation, data sets and modeling that support a timely assessment of Earth-directed coronal mass ejections are improving, but there remains a gap in the ability of forecasters to predict the occurrence of a coronal mass ejection ahead of time. We assess over 50 years of observational studies of coronal mass ejection source regions, and their evolution toward eruption, in order to provide guidance for those working in space weather forecasting. The aim being to provide an overview of the indicators that a region may have: (a) already produced a coronal mass ejection, that is, not identified in coronagraph images in a timely way, and (b) that a region may be likely to produce a CME in the near future. Checklists are provided as a practical tool for day-to-day forecasting.