Multiwavelength spectropolarimetric observations of an Ellerman bomb

Abstract

Context. Ellerman bombs (EBs) are enhanced emission in the wings of the Hα line in the solar spectrum. Aims. We study the structure of an EB in the photosphere and chromosphere.Methods. We analyze simultaneous observations of four chromospheric lines (Hα, Ca ii H, Ca ii IR 854 nm, and He i 1083 nm) as well as two photospheric lines (Fe i 630 and Si i 1082.7 nm) along with high-cadence 160 and 170 nm ultraviolet (UV) continuum filtergrams. Full Stokes data from the Helioseismic and Magnetic Imager (HMI) are used to trace the temporal evolution of the magnetic structure.Results. We identify the EB by excess emission in the wings of the Hα line, a brightening in the UV continuum, and large emission peaks in the core of the two Ca ii lines. The EB shows a blueshift in all chromospheric lines, while no shifts are observed in the photospheric lines. The blueshift in the chromospheric layer causes very asymmetric emission peaks in the Ca ii H line. The photospheric Si i spectral line shows a shallower line depth at the location of the EB. The UV continuum maps show that the EB was substantially brighter than its surroundings for about 30 min. The continuum contrast of the EB from 170 nm to 1080 nm shows a power-law dependency on the wavelength. The temperature enhancement amounts to 130 K in the low photosphere and 400 K at the temperature minimum level. This temperature excess is also seen in an LTE inversion of the Ca ii spectra. The total thermal and radiative energy content of the EB is about 10 20 J and 10 18 J in the photosphere and chromosphere, respectively. The HMI data hints at a photospheric magnetic flux cancellation as the driver of the EB. Conclusions. Ellerman bombs release the energy in a height range of several pressure scale heights around the temperature minimum such that they affect both the photosphere and the lower chromosphere.

Observations of Ellerman bomb emission features in He i D3and He i 10 830 Å

“…Rezaei & Beck (2015) have observed EBs in He i 10830 Å, but only reported co-spatial absorption. They propose to use the line to reject false EB identifications by showing emission profiles.…”

“…Our detections strongly discourage this idea. There is a variety of reasons for why Rezaei & Beck (2015) have not been able to detect the helium emission signals. First of all, they give a value of 1 as spatial resolution for their observations.…”

“…To our knowledge, no other observations of EBs in He i D 3 have been published. Rezaei & Beck (2015) observed EBs in He i 10830 Å, but only found co-spatial absorption with the EBs. However, using high-spatial resolution SST/TRIPPEL spectra, we have for the first time detected wing emission in He i D 3 and He i 10830 Å associated with EBs.…”

Capabilities of bisector analysis of the Si I 10 827 Å line for estimating line-of-sight velocities in the quiet Sun

“…Kuckein et al 2012;Xu et al 2012), Ellerman bombs (e.g. Rezaei & Beck 2015), sunspots and pores (e.g. Xu et al 2010;Joshi 2014), flares (Judge et al 2014;Kuckein et al 2015), or independently, for example, in small-scale magnetic bright points (Kuckein 2019) or sunspots (e.g.…”

Photospheric Response to an Ellerman Bomb-like Event—An Analogy of Sunrise/IMaX Observations and MHD Simulations

“…They are defined as transient brightenings of the extended wings of the Hα line, but leave signatures also in Ca II H and Ca II IR 854 nm Rezaei & Beck 2015) and sometimes even in observables which should sample orders of magnitude higher temperatures than the former Tian et al 2016). Observations show that EBs are almost exclusively formed in young emerging active regions, usually between spots/pores where the emergence of serpentine field lines takes place.…”