Detection of opposite polarities in a sunspot light bridge: evidence of low-altitude magnetic reconnection

Abstract

A multi-wavelength photometric analysis was performed in order to study the sub-structure of a sunspot light bridge in the photosphere and the chromosphere. Active region NOAA 8350 was observed on 1998 October 8. The data consist of a 100 min time series of 2D spectral scans of the lines FeI 5576, H-alpha 6563, FeI 6302.5, and continuum images at 5571. We recorded line-of-sight magnetograms in 6302.5. The observations were taken at the Dunn Solar Telescope at U. S. National Solar Observatory, Sacramento Peak. We find evidence for plasma ejection from a light bridge followed by Ellerman bombs. Magnetograms of the same region reveal opposite polarity in light-bridge with respect to the umbra. These facts support the notion that low altitude magnetic reconnection can result in the magnetic cancellation as observed in the photosphere.