Abstract
Using a substorm onset list from the Imager for Magnetopause to Aurora
Global Exploration (IMAGE) and Polar satellite images, we have
constructed a new dataset of 63 substorm onsets observed in both
hemispheres and their locations. We find that incorporating the history
of the interplanetary magnetic field (IMF) improves the predictive power
of IMF By in explaining conjugate displacement in Magnetic Local Time
(MLT). Our dataset, approximately five times larger than in previous
studies, enhances statistical power and focuses on the substorm onset
feature. This allows for better correlation of IMF By with MLT conjugate
displacement (ΔMLT), since it has been shown that IMF-induced By tends
to diminish as substorms progress. In line with previous work, we find a
linear relationship between IMF By and ΔMLT, though with a shallower
gradient. Additionally, we analyse predictors of conjugate displacement
in Magnetic Latitude (ΔMLat), showing that dipole tilt (ψ) is the
strongest predictor. However, we find that this relationship is not
strictly linear, and that a larger dataset and a better understanding of
the physical mechanisms are needed to more accurately capture the exact
functional relationship between ψ and ΔMLat.