Magnetic field structure taken from the global NLFFF evolutionary model in the time period prior to the eruption of the stealth event that occurred on 2015 January 3. The panels show the radial magnetic field of the photosphere (grey) where white (black) regions correspond to positive (negative) magnetic field. The red lines are representative magnetic field lines from the model to show the configuration of the coronal magnetic field. The panels are plotted in a co-rotating frame at the Carrington rate where the corresponding Carrington Rotation is given in the bottom left. Panel a: the initial potential condition (day 1) of the model is shown where central meridian is at 215° longitude. For panels b–d central meridian is at 0° longitude.