Quantifying the uncertainty in CME kinematics derived from geometric
modelling of Heliospheric Imager data
Abstract
Geometric modelling of Coronal Mass Ejections (CMEs) is a widely used
tool for assessing their kinematic evolution. Furthermore, techniques
based on geometric modelling, such as ELEvoHI, are being developed into
forecast tools for space weather prediction. These models assume that
solar wind structure does not affect the evolution of the CME, which is
an unquantified source of uncertainty.
We use a large number of Cone CME simulations with the HUXt solar wind
model to quantify the scale of uncertainty introduced into geometric
modelling and the ELEvoHI CME arrival times by solar wind structure. We
produce a database of simulations, representing an average, a fast, and
an extreme CME scenario, each independently propagating through 100
different ambient solar wind environments. Synthetic heliospheric imager
observations of these simulations are then used with a range of
geometric models to estimate the CME kinematics. The errors of geometric
modelling depend on the location of the observer, but do not seem to
depend on the CME scenario. In general, geometric models are biased
towards predicting CME apex distances that are larger than the true
value. For these CME scenarios, geometric modelling errors are minimised
for an observer in the L5 region. Furthermore, geometric modelling
errors increase with the level of solar wind structure in the path of
the CME. The ELEvoHI arrival time errors are minimised for an observer
in the L5 region, with mean absolute arrival time errors of 8.2±1.2h,
8.3±1.0h, and 5.8±0.9h for the average, fast, and extreme CME scenarios