Microflare activity driven by forced magnetic reconnection

Abstract

High cadence, multiwavelength, optical observations of a solar active region, obtained with the Swedish Solar Telescope, are presented. Two magnetic bright points are seen to separate in opposite directions at a constant velocity of 2.8kms-1. After a separation distance of ≈4400km is reached, multiple Ellerman bombs are observed in both Hα and Ca-K images. As a result of the Ellerman bombs, periodic velocity perturbations in the vicinity of the magnetic neutral line, derived from simultaneous Michelson Doppler Imager data, are generated with amplitude ±6kms-1 and wavelength 1000km. The velocity oscillations are followed by an impulsive brightening visible in Hα and Ca-K, with a peak intensity enhancement of 63%. We interpret these velocity perturbations as the magnetic field deformation necessary to trigger forced reconnection. A time delay of ≈3 minutes between the Hα-wing and Ca-K observations indicates that the observed magnetic reconnection occurs at a height of 200km above the solar surface. These observations are consistent with theoretical predictions and provide the first observational evidence of microflare activity driven by forced magnetic reconnection. © 2010. The American Astronomical Society. All rights reserved.