Forecasting the magnetic vectors within a CME at L1 by using solar observations.
Thursday, 18 December 2014
The direction of magnetic vectors within coronal mass ejections has important consequences to forecasting terrestrial behaviour, however forecasting these vectors remains predominately elusive. Here, we report that a simplified system is capable of replicating the broad field rotations seen within flux rope CMEs at L1 monitors. The predictions are performed under three main themes: 1) The majority of the field rotations can be simplified to the constant-alpha force-free (CAFF) flux model first implemented circa 1990. 2) The helicity will follow the Bothmer & Schwenn system that relies on a reliable helicity prediction of active regions during solar cycle. Which has been recently confirmed by Wang [2013 ApJ]. 3) The majority of the distortions, deflections and rotations will have already occurred within coronagraphic field of view, thereby allowing the creation of a projected “volume-of-influence” on the Sun, from which Earth’s position relative to the CME can be estimated. This presentation will compare predicted results to the observations from 7 CME events and then estimate the sources of uncertainty. As an example, the difference in robust statistics from 2 solar cycles of CAFF model fittings for the field magnitude will be compared to estimates generated from simulated CME-sheaths within forecasting Enlil runs.
The figure displays an example field vector forecast from the techniques employed above.