The Origin and Early Evolution of a Bipolar Magnetic Region in the Solar Photosphere

Abstract

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 Ω-shaped loop of a flux tube of strong magnetic field, and an in situ mechanism of magnetic-field amplification and structuring should operate in this case.

A Magnetic Reconnection model for Hot Explosions in the Cool Atmosphere of the Sun

“…The small scale flux emergences with a maximum strength of several hundred Gauss are frequently observed in reconnection events of UV bursts and EBs (e.g., Wang et al 2020;Chen et al 2019a), the much stronger magnetic fields of over several thousand Gauss have also been observed in active regions(e.g., Getling et al 2019;Liu et al 2020;Leenaarts et al 2018;Yan et al 2017Yan et al , 2020. Therefore, the strength of reconnection magnetic fields in our simulations are reasonable.…”

“…Different scales of magnetic flux emergence happen all the time. The observational results indicate that the emerged magnetic fields can be as strong as several thousand Gauss in the photosphere(e.g., Yan et al 2017;Leenaarts et al 2018;Getling et al 2019;Liu et al 2020;Yan et al 2020). Magnetic reconnection can happen between the emerging magnetic fields with opposite directions, or when the emerged ones interact with the back ground magnetic fields.…”

Visualization of the movements of natural objects based on remote sensing data

“…As the process progresses, it is necessary to track the trajectory of each trial cork. We considered a series of images of different duration from 2 to 4 hours with an interval of 135 s. between frames [6].…”

Evolution of the Source of a Photospheric Active Region

“…Однако современные наблюдения не подтверждают представление о формировании активной области как результат «всплытия» компактного магнитного образования. [1,2].…”