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.
KeywordsActive regions, magnetic fields Magnetic fields, photosphere Solar cycle, models
We acknowledge the Leverhulme Trust for funding the “Probing the Sun: inside and out” project upon which this research is based. ARY thanks STFC for financial support through consortium grant ST/K001043/1. The research leading to these results has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration under Grant Agreement No. 284461 (eHEROES project). LvDG acknowledges the Hungarian government for grant OTKA K 109276. DB and LvDG thanks STFC for support under Consolidated Grant ST/H00260/1. This work utilises data obtained by the Global Oscillation Network Group (GONG) program, managed by the National Solar Observatory, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. The data were acquired by instruments operated by the Big Bear Solar Observatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de Astrofísica de Canarias, and Cerro Tololo Interamerican Observatory. We thank Duncan Mackay for reading an initial draft and the referee for helpful suggestions.
- Arge, C.N., Henney, C.J., Koller, J., Compeau, C.R., Young, S., MacKenzie, D., Fay, A., Harvey, J.W.: 2010, Air Force Data Assimilative Photospheric Flux Transport (ADAPT) model. In: Maksimovic, M., et al. (eds.) Twelfth International Solar Wind Conference, CP, 1216, AIP, Melville, 343. DOI. ADS. Google Scholar
- DeVore, C.R., 1986, Theory and simulation of the evolution of the large-scale solar magnetic field, PhD thesis, Princeton Univ. Google Scholar
- Zolotova, N.V., Ponyavin, D.I.: 2012, Reconstruction of magnetic field surges to the poles from sunspot impulses. In: Mandrini, C.H., Webb, D.F. (eds.) Comparative Magnetic Minima: Characterizing quiet times in the Sun and Stars, IAU Symp, 286, Cambridge University Press, Cambridge, 88, DOI. ADS. Google Scholar