ELLERMAN BOMBS AT HIGH RESOLUTION. I. MORPHOLOGICAL EVIDENCE FOR PHOTOSPHERIC RECONNECTION

Abstract

High-resolution imaging-spectroscopy movies of solar active region NOAA 10998\nobtained with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m\nSolar Telescope show very bright, rapidly flickering, flame-like features that\nappear intermittently in the wings of the Balmer H-alpha line in a region with\nmoat flows and likely some flux emergence. They show up at regular H-alpha\nblue-wing bright points that outline magnetic network, but flare upward with\nmuch larger brightness and distinct "jet" morphology seen from aside in the\nlimbward view of these movies. We classify these features as Ellerman bombs and\npresent a morphological study of their appearance at the unprecedented spatial,\ntemporal, and spectral resolution of these observations. The bombs appear along\nmagnetic network with footpoint extents up to 900km. They show apparent travel\naway from the spot along the pre-existing network at speeds of about 1 km/s.\nThe bombs flare repetitively with much rapid variation at time scales of\nseconds only, in the form of upward jet-shaped brightness features. These reach\nheights of 600-1200km and tend to show blueshifts; some show bi-directional\nDoppler signature, and some seem accompanied with an H-alpha surge. They are\nnot seen in the core of H-alpha due to shielding by overlying chromospheric\nfibrils. The network where they originate has normal properties. The morphology\nof these jets strongly supports deep-seated photospheric reconnection of\nemergent or moat-driven magnetic flux with pre-existing strong vertical network\nfields as the mechanism underlying the Ellerman bomb phenomenon.\n