arXiv subjects

Fangfang Qiao

Publications and source records attributed to Fangfang Qiao.

2 recordsLinked to original sources

arXiv2026

Fine Structure and Formation Mechanism of a Sunspot Bipolar Light Bridge in NOAA AR 13663

Bipolar Light Bridges (BLBs) are bright regions located between sunspot umbrae of opposite magnetic polarity. They are typically characterized by strong magnetic fields and intense flows, which are believed to be closely associated with major solar flares. Despite their importance, their fine structure, formation and evolution remain poorly understood. In this work, we analyze the observations of a well-defined BLB obtained by the Goode Solar Telescope at the Big Bear Solar Observatory and the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory. The high-resolution GST observations reveal that the BLB is composed of fine, penumbral filament-like structures with widths of approximately 100-150 km. The corresponding Doppler velocity maps present a stable pattern of spatially adjacent red- and blueshifted patches within the BLB throughout the 5.5-hour GST observation. HMI observations show that the BLB arises from the converging and shearing motions of sunspots with opposite polarities. Penumbral regions originating from different polarities gradually evolve and interact, eventually forming the BLB. The observed Doppler velocity pattern, characterized by red- and blueshifted patches, can be interpreted as a projection effect of the Evershed flow within the penumbrae. Therefore, we argue that the BLB is formed through the compression and stretching of penumbral structures from oppositely polarized sunspots.

astro-ph.SR↗

arXiv2024

Three types of solar coronal rain during magnetic reconnection between open and closed magnetic structures

Coronal rain (CR) is a crucial part of the mass cycle between the corona and chromosphere. It includes the flare-driven CR and two types of quiescent CR separately along the non-flaring active region closed loops and along the open structures, labeled as types I, II, and III CR, respectively. Among them, types I and III CR are generally associated with magnetic reconnection. In this study, employing data taken by the Solar Dynamics Observatory (SDO) and the Solar Upper Transition Region Imager (SUTRI) on 2022 October 11, we report three types of CR during an interchange reconnection between open and closed magnetic filed structures above the southeastern solar limb. The open and closed structures converge, with the formation of current sheet at the interface, and reconnect. The newly-formed closed and open structures then recede from the reconnection region. During the reconnection, coronal condensation occurs along the reconnecting closed loops, and falls toward the solar surface along both loop legs as the type II CR. Subsequently, condensation happens in the newly-formed closed loops, and moves down toward the solar surface along both loop legs as the type I CR. Magnetic dips of the reconnecting open structures form during the reconnection. In the dips, condensation occurs, and propagates along the open structures toward the solar surface as the type III CR. Our results suggest that the reconnection rate may be crucial for the formation of types I and III CR during the reconnection.

astro-ph.SR↗