Formation of Ellerman bombs due to 3D flux emergence

School of Mathematics and Statistics, University of St. Andrews, North Haugh, St. Andrews, Fife, KY16 9SS, UK e-mail: [vasilis;alan]@mcs.st-and.ac.uk

Received: 8 May 2009
Accepted: 21 October 2009

Abstract

Aims. We investigate the emergence of a “sea-serpent” magnetic field into the outer solar atmosphere and the connection between undulating fieldlines and formation of Ellerman bombs.

Methods. We perform 3D numerical experiments solving the time-dependent and resistive MHD equations.

Results. A sub-photospheric magnetic flux sheet develops undulations due to the Parker instability. It rises from the convectively unstable sub-photospheric layer and emerges into the highly stratified atmosphere through successive reconnection events along the undulating system. Brightenings with the characteristics of Ellerman bombs are produced due to reconnection, which occurs during the emergence of the field. At an advanced stage of the evolution of the system, the resistive emergence leads to the formation of long, arch-like magnetic fields that expand into the corona. The enhancement of the magnetic field at the low atmosphere and episodes of emergence of new magnetic flux are also discussed.