Dynamic properties of bright points in an active region

TL;DR

This study investigates the dynamic properties of bright points in an active solar region, revealing that magnetic flux influences their size, velocity, and lifetime, with active regions showing larger, slower, and longer-lived bright points compared to quiet Sun areas.

Contribution

It provides the first detailed comparison of bright point dynamics between active regions and quiet Sun, highlighting the impact of magnetic flux on their properties.

Findings

Active region BPs have lower average velocities (~0.6 km/s) than quiet Sun BPs (~0.9 km/s).

Bright points in active regions are approximately 21% larger and have longer lifetimes (~132s) than those in quiet regions (~88s).

The diffusion index (gamma) is estimated at ~1.2 across regions, indicating similar diffusion behavior.

Abstract

Context. Bright points (BPs) are small-scale, magnetic features ubiquitous across the solar surface. Previously, we have observed and noted their properties for quiet Sun regions. Here, we determine the dynamic properties of BPs using simultaneous quiet Sun and active region data. Methods. High spatial and temporal resolution G-band observations of active region AR11372 were obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope. Three subfields of varying polarity and magnetic flux density were selected with the aid of magnetograms obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. Bright points within these subfields were subsequently tracked and analysed. Results. It is found that BPs within active regions display attenuated velocity distributions with an average horizontal velocity of ~0.6 km/s, compared to the quiet region which had an average velocity of 0.9 km/s. Active region BPs are also ~21% larger than quiet region BPs and have longer average lifetimes (~132s) than their quiet region counterparts (88 s). No preferential flow directions are observed within the active region subfields. The diffusion index (gamma) is estimated at ~1.2 for the three regions. Conclusions. We confirm that the dynamic properties of BPs arise predominately from convective motions. The presence of stronger field strengths within active regions is the likely reason behind the varying properties observed. We believe that larger amounts of magnetic flux will attenuate BP velocities by a combination of restricting motion within the intergranular lanes and by increasing the number of stagnation points produced by inhibited convection. Larger BPs are found in regions of higher magnetic flux density and we believe that lifetimes increase in active regions as the magnetic flux stabilises the BPs.