Source of a Prominent Poleward Surge During Solar Cycle 24

TL;DR

This study investigates the origin of a significant poleward surge during Solar Cycle 24 using a new flux assimilation technique, revealing it mainly stems from specific high-latitude active regions with opposing dipole moments.

Contribution

A novel method for assimilating magnetic flux regions into flux transport models was developed, enabling detailed analysis of surge origins during Solar Cycle 24.

Findings

Surge originated mainly from a bipolar active region in late 2010 to early 2011.

The active region had a strong axial dipole moment opposite to Joy's law.

High-latitude location limited its long-term impact on polar fields.

Abstract

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 of its location at high latitude. This is in accordance with previous flux transport models.