Photospheric plasma and magnetic field dynamics during the formation of solar AR 11190^⋆

¹ IGAM, Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
e-mail: jose.campos-rozo@uni-graz.at
² Universidad Nacional de Colombia, Observatorio Astronómico Nacional, Ed. 413 Bogotá, Colombia
e-mail: svargasd@unal.edu.co
³ Instituto de Astrofísica de Andalucía IAA-CSIC, 18008 Granada, Spain
e-mail: dominik.utz@uni-graz.at
⁴ Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, 3001 Leuven, Belgium

Received: 2 February 2018
Accepted: 15 December 2018

Abstract

Context. The Sun features on its surface typical flow patterns called the granulation, mesogranulation, and supergranulation. These patterns arise due to convective flows transporting energy from the interior of the Sun to its surface. The other well known elements structuring the solar photosphere are magnetic fields arranged from single, isolated, small-scale flux tubes to large and extended regions visible as sunspots and active regions.

Aims. In this paper we will shed light on the interaction between the convective flows in large-scale cells as well as the large-scale magnetic fields in active regions, and investigate in detail the statistical distribution of flow velocities during the evolution and formation of National Oceanic and Atmospheric Administration active region 11190.

Methods. To do so, we employed local correlation tracking methods on data obtained by the Solar Dynamics Observatory in the continuum as well as on processed line-of-sight magnetograms.

Results. We find that the flow fields in an active region can be modelled by a two-component distribution. One component is very stable, follows a Rayleigh distribution, and can be assigned to the background flows, whilst the other component is variable in strength and velocity range and can be attributed to the flux emergence visible both in the continuum maps as well as magnetograms. Generally, the plasma flows, as seen by the distribution of the magnitude of the velocity, follow a Rayleigh distribution even through the time of formation of active regions. However, at certain moments of large-scale fast flux emergence, a second component featuring higher velocities is formed in the velocity magnitudes distribution.

Conclusions. The plasma flows are generally highly correlated to the motion of magnetic elements and vice versa except during the times of fast magnetic flux emergence as observed by rising magnetic elements. At these times, the magnetic fields are found to move faster than the corresponding plasma.