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

Abstract

A multiwavelength 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 Fe i 5576 A, Hα 6563 A, Fe i 6302.5 A, and continuum images at 5571 A. We recorded line-of-sight magnetograms in 6302.5 A. The observations were taken at the Dunn Solar Telescope at US 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.