The origin of dark lane on sunspot’s light bridge

Abstract

Light bridges (LBs), embedded in sunspots, appear as elongated narrow bright features, in contrast to the surrounding dark sunspot umbra or penumbra. Under high-resolution observations, dark lanes were reported along the spine of LBs. Although numerical modeling explains the basic physical properties of LBs , how and where the dark lanes form remain incomprehensible from the observational aspect. The multiwavelength observations obtained by the Goode Solar Telescope (GST) at Big Bear Solar Observatory (BBSO), show that the dark lanes are prominent in the H \(\alpha \) , visible continuum and near infrared (NIR) line core. However, they are absent from the NIR continuum, which is formed about 30 km below the photosphere. These results provide altitude data for the layered structure and suggest that the dark lanes located above this region originate in the deep photosphere.