Dynamic properties of bright points in an active region

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. Aims. The aim of this paper is to compare the properties of BPs in both active and quiet Sun regions and to determine any difference in the dynamics and general properties of BPs as a result of the varying magnetic activity within these two regions. 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 −1 , compared to the quiet region which had an average velocity of 0.9 km s −1 . Active region BPs are also ∼21% larger than quiet region BPs and have longer average lifetimes (∼132 s) than their quiet region counterparts (88 s). No preferential flow directions are observed within the active region subfields. The diffusion index (γ) 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.

Characterizing motion types ofG-band bright points in the quiet Sun

“…Giannattasio et al (2014) found γ = 1.27±0.05 and γ = 1.08±0.11 in network (at smaller and larger scales, respectively), and γ = 1.44±0.08 in internetwork regions. Keys et al (2014) estimated γ of ∼1.2 for both quiet region and active region, then confirmed that the dynamic properties of GBPs arise predominately from convective motions. Our result is in qualitative agreement with recent studies of diffusion.…”

“…Recent studies show that a GBPs motion is determined mainly by the buffeting motion of granules. The convective motions of granules push and squeeze GBPs violently, resulting in chaotic motion of GBPs (Berger et al 1998a;van Ballegooijen et al 1998;Möstl et al 2006;Giannattasio et al 2013;Keys et al 2014). These smallscale motions are thought to play an important role in heating the upper solar atmosphere by twisting and braiding magnetic flux tubes, generating kinetic, Alfvén waves and so on (Cranmer 2002;Cranmer & van Ballegooien 2005;Klimchuk 2006;de Wijn et al 2009;Zhao et al 2009;Balmaceda et al 2010).…”

Photospheric Observations of Surface and Body Modes in Solar Magnetic Pores

“…Previous work (Keys et al 2014) on the 2011 December 10 data analysed here used a tracking algorithm to study the motion of MBPs in this particular active region. Our study came to the conclusion that the MBPs did not have a preferential direction of motion, that the diffusion of MBPs did not differ between Figure 8.…”

Super-diffusion versus competitive advection: a simulation

“…On the observational side, a viable way to study the convective flows on the solar surface are the small scale magnetic field elements since they are ubiquitous (Romano et al 2012;Keys et al 2014) and they (or their proxies, see Steiner et al 2001;Uitenbroek & Tritschler 2006) are often used as tracers of the plasma flows (e.g. Bonet et al 2008;Berrilli et al 2013Berrilli et al , 2014.…”