Abstract
We statistically studied the transport of magnetic flux in and around sunspots using a magnetic-element tracking technique to investigate whether sunspot-decay processes are isotropic. Using this method, we detected moving magnetic features (MMFs). The observed radius of an MMFs region was approximately 1.7 times the sunspot radius; furthermore, the average apparent velocity of MMFs was statistically estimated to be approximately \(350~\mbox{m}\,\mbox{s}^{-1}\). We determined that the leading sunspots transport approximately 5% more magnetic flux to the Equator side than to the Pole side of the sunspots. In addition, the leading sunspots transport approximately 3% more magnetic flux to the back (East) than to the front (West) of the sunspots. On the other hand, the following sunspots do not show the magnetic-flux transport asymmetry. The statistics might not be sufficient for the analysis of the following sunspots. These asymmetries of magnetic flux transport might contribute to the cross-equatorial transport of net magnetic flux, which is an important physical quantity of polar magnetic-field reversal.
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Acknowledgments
We would like to thank the reviewer for useful comments that helped improving the manuscript. The authors thank H. Iijima, K. Kusano, H. Hotta, and Y. Iida for fruitful discussions. This work was partially supported by the Grant-in-Aid for 17K14401 and 15H05816. This work was also partially supported by the ISEE CICR International Workshop program, and the authors thank all members of the workshop. This study was supported by the NINS program for cross-disciplinary study on turbulence, transport, and heating dynamics in laboratory and solar/astrophysical plasmas: SoLaBo-X (Grant Numbers 01321802 and 01311904). This research was also supported by the Basic Science Research Program through the NRF, funded by the Ministry of Education (NRF2019R1C1C1004778, NRF-2020R1C1C1003892). A part of this study was conducted using the computational resources of the Center for Integrated Data Science, Institute for Space–Earth Environmental Research, Nagoya University.
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Imada, S., Kato, S. & Fujiyama, M. Statistical Analysis of Asymmetric Sunspot Decay Observed by Hinode. Sol Phys 295, 154 (2020). https://doi.org/10.1007/s11207-020-01724-x
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DOI: https://doi.org/10.1007/s11207-020-01724-x