Source of a prominent poleward surge during Solar Cycle 24.

As an observational case study, we consider the origin of a prominent poleward surge of leading polarity, visible in the magnetic butterfly diagram during Solar Cycle 24. A new technique is developed for assimilating individual regions of strong magnetic flux into a surface-flux transport model. By isolating the contribution of each of these regions, the model shows the surge to originate primarily in a single high-latitude activity group consisting of a bipolar active region present in Carrington Rotations 2104 – 05 (November 2010 – January 2011) and a multipolar active region in Rotations 2107 – 08 (February – April 2011). This group had a strong axial dipole moment opposed to Joy’s law. On the other hand, the modelling suggests that the transient influence of this group on the butterfly diagram will not be matched by a large long-term contribution to the polar field because it is located at high latitude. This is in accordance with previous flux-transport models