The origin and early evolution of a bipolar magnetic region in the solar photosphere
| Autor: | A. A. Buchnev, A. V. Getling |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Physics
Sunspot Photosphere 010504 meteorology & atmospheric sciences Flux tube Field (physics) FOS: Physical sciences Astronomy and Astrophysics Astrophysics 01 natural sciences Magnetic flux Magnetic field Amplitude Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics Supergranulation 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences |
| Popis: | Finding the formation mechanisms for bipolar configurations of strong local magnetic field under control of the relatively weak global magnetic field of the Sun is a key problem of the physics of solar activity. This study is aimed at discriminating whether the magnetic field or fluid motion plays a primary, active role in this process. The very origin and early development stage of Active Region 12548 are investigated based on SDO/HMI observations of 2016 May 20--25. Full-vector magnetic and velocity fields are analyzed in parallel. The leading and trailing magnetic polarities are found to grow asymmetrically in terms of their amplitude, magnetic flux, and the time variation of these quantities. The leading-polarity magnetic element originates as a compact feature against the background of a distributed trailing-polarity field, with an already existing trailing-polarity magnetic element. No signs of strong horizontal magnetic fields are detected between the two magnetic poles. No predominant upflow between their future locations precedes the origin of this bipolar magnetic region (BMR); instead, upflows and downflows are mixed, with some prevalence of downflows. Any signs of a large-scale horizontal divergent flow from the area where the BMR develops are missing; in contrast, a normal supergranulation and mesogranulation pattern is preserved. This scenario of early BMR evolution is in strong contradiction with the expectations based on the model of a rising $\Omega$-shaped loop of a flux tube of strong magnetic field, and an \emph{in situ} mechanism of magnetic-field amplification and structuring should operate in this case. Comment: 11 pages, 5 figures |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|