Abstracts Details


First Name * : Viggo
Last Name * : Hansteen
Affiliation * : BAERI/LMSAL
Abstract Type * : Oral
Title * : Ellerman bombs and UV bursts: reconnection at different atmospheric layers
Author(s) * : Viggo Hansteen, Ada Ortiz, Daniel Nobrega, Luc Rouppe van der Voort
Abstract Session * : Thermal and magnetic coupling through the atmosphere
Abstract * : The emergence of magnetic flux through the photosphere and into the outer solar atmosphere produces, amongst many other dynamical phenomena, the appearance of Ellerman bombs (EBs) in the photosphere. EBs are observed in the wings of H(alpha) and are highly likely to be due to reconnection in the photosphere, below the chromospheric canopy. Signs of the reconnection process are also observed in several other spectral lines, typical of the chromosphere or the transition region. An example are the UV bursts observed in the transition region lines of Si IV and the upper chromospheric lines of Mg II. In this work we analyze high cadence, high resolution coordinated observations between the Swedish 1-m Solar Telescope (SST) and the Interface Region Imaging Spectrograph (IRIS) spacecraft in order to study the possible relationship between reconnection events at different layers in the atmosphere and, in particular, the timing history between them. H(alpha) images from the SST provide us with the positions, timings and trajectories of EBs in an emerging flux region. Simultaneous, co-aligned IRIS slit-jaw images at 1330 (C II, transition region), 1400 (Si IV, transition region) and 2796 (Mg II k, core, upper chromosphere) Å, as well as spectroscopy in the far and near ultraviolet from the fast spectrograph raster, allow us to study the possible chromospheric/transition region counterparts of those photospheric EBs. Our main goal is to study whether there is a temporal and spatial relationship between the appearance of an EB and the appearance of a UV burst and the connection of these dynamical phenomena to the appearance of surges in the chromosphere. We also investigate in detail the properties of an extended UV burst and their variations across the burst domain. Our results suggest a scenario where simultaneous and co-spatial EBs and UV bursts are part of the same reconnection system occurring sequentially along a vertical or nearly vertical current sheet. Heating and bidirectional jets trace the location where reconnection takes place. This scenario is in agreement with the most recent 3D numerical experiments modeling flux emergence.