Field distribution of magnetograms from simulations of active region formation

¹ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Surrey, RH5 6NT, UK
e-mail: sallydacie@gmail.com
² Observatoire de Paris, LESIA, UMR 8109 (CNRS), 92195 Meudon-Principal Cedex, France
³ Konkoly Observatory of the Hungarian Academy of Sciences, 1121 Budapest, Hungary
⁴ US Naval Research Laboratory, 4555 Overlook Avenue, SW Washington, DC 20375, USA
⁵ NASA Goddard Space Flight Center, Greenbelt MD, USA
⁶ School of Mathematics and Statistics, University of Glasgow, Glasgow G12 8QW, UK
⁷ Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street Bldg. 252, Palo Alto, CA 94304, USA

Received: 11 March 2017
Accepted: 13 July 2017

Abstract

Context. The evolution of the photospheric magnetic field distributions (probability densities) has previously been derived for a set of active regions. Photospheric field distributions are a consequence of physical processes that are difficult to determine from observations alone.

Aims. We analyse simulated magnetograms from numerical simulations, which model the emergence and decay of active regions. These simulations have different experimental set-ups and include different physical processes, allowing us to investigate the relative importance of convection, magnetic buoyancy, magnetic twist, and braiding for flux emergence.

Methods. We specifically studied the photospheric field distributions (probability densities found with a kernel density estimation analysis) and compared the results with those found from observations.

Results. Simulations including convection most accurately reproduce the observed evolution of the photospheric field distributions during active region evolution.

Conclusions. This indicates that convection may play an important role during the decay phase and also during the formation of active regions, particularly for low flux density values.