http://arxiv.org/abs/1805.06486
The very conception and early development stage of AR 12548 are investigated based on SDO/HMI observations of 20–25 May 2016. Full-vector magnetic and velocity fields are analysed in parallel. In the growing bipolar magnetic (BMR), the leading-polarity magnetic element nucleates as a compact feature against the background of a distributed trailing-polarity field, in which a germ of the trailing-polarity element is already present. Both magnetic elements give rise to a couple of pores, which then evolves into a bipolar sunspot group. The growth of the leading (negative) polarity sets in abruptly and occurs rapidly while the trailing (positive) polarity grows smoothly and more slowly. There is also similar dissymmetry between the time variations of the negative and positive magnetic fluxes through some area encompassing the BMR. No signs of strong horizontal magnetic fields are detected between the growing leading and trailing magnetic poles of the BMR. No predominant upflow between the future locations of the magnetic poles precedes the origin of the BMR; instead, upflows and downflows are mixed, with some prevalence of downflows. Any signs of a large-scale horizontal divergent flow from the area when the BMR develops are missing; in contrast, a regular supergranulation and mesogranulation pattern remains intact. The observed scenario of early BMR evolution is in strong contradiction with the expectations following from the model of rising $\Omega$-shaped loop of a flux tube of strong magnetic field.
A. Getling and A. Buchnev
Fri, 18 May 18
30/51
Comments: 16 pages, 7 figures
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