Search Publications
A publicly available simulation of an enhanced network region of the Sun
De Pontieu, Bart; Carlsson, Mats; Hansteen, Viggo H. +2 more
Context. The solar chromosphere is the interface between the solar surface and the solar corona. Modelling of this region is difficult because it represents the transition from optically thick to thin radiation escape, from gas-pressure domination to magnetic-pressure domination, from a neutral to an ionised state, from MHD to plasma physics, and …
Hα features with hot onsets. I. Ellerman bombs
Rutten, R. J.
Ellerman bombs are transient brightenings of the wings of the Balmer lines that uniquely mark reconnection in the solar photosphere. They are also bright in strong Ca II and ultraviolet lines and in ultraviolet continua, but they are not visible in the optical continuum and the Na I D and Mg I b lines. These discordant visibilities invalidate all …
Reconnection brightenings in the quiet solar photosphere
Rouppe van der Voort, Luc H. M.; Rutten, Robert J.; Vissers, Gregal J. M.
We describe a new quiet-Sun phenomenon which we call quiet-Sun Ellerman-like brightenings (QSEB). QSEBs are similar to Ellerman bombs (EB) in some respects but differ significantly in others. EBs are transient brightenings of the wings of the Balmer Hα line that mark strong-field photospheric reconnection in complex active regions. QSEBs are simil…
Density diagnostics derived from the O iv and S iv intercombination lines observed by IRIS
Mason, H. E.; Del Zanna, G.; Reeves, K. K. +3 more
The intensity of the O iv 2s2 2p 2P-2s2p24P and S iv 3 s2 3p 2P-3s 3p24 P intercombination lines around 1400 Å observed with the Interface Region Imaging Spectrograph (IRIS) provide a useful tool to diagnose the electron number density (Ne) in the so…
Height formation of bright points observed by IRIS in Mg II line wings during flux emergence
Heinzel, P.; Schmieder, B.; Berlicki, A. +3 more
Context. A flux emergence in the active region AR 111850 was observed on September 24, 2013 with the Interface Region Imaging Spectrograph (IRIS). Many bright points are associated with the new emerging flux and show enhancement brightening in the UV spectra.
Aims: The aim of this work is to compute the altitude formation of the compact brigh…
A closer look at a coronal loop rooted in a sunspot umbra
Peter, H.; Chitta, L. P.; Young, P. R.
Context. Extreme UV (EUV) and X-ray loops in the solar corona connect regions of enhanced magnetic activity, but they are not usually rooted in the dark umbrae of sunspots because the strong magnetic field found there suppresses convection. This means that the Poynting flux of magnetic energy into the upper atmosphere is not significant within the…
The cause of spatial structure in solar He I 1083 nm multiplet images
Joshi, Jayant; Carlsson, Mats; Leenaarts, Jorrit +2 more
Context. The He I 1083 nm is a powerful diagnostic for inferring properties of the upper solar chromosphere, in particular for the magnetic field. The basic formation of the line in one-dimensional models is well understood, but the influence of the complex three-dimensional structure of the chromosphere and corona has however never been investiga…
First simultaneous SST/CRISP and IRIS observations of a small-scale quiet Sun vortex
Doyle, J. G.; Scullion, E.; Tziotziou, K. +3 more
Context. Ubiquitous small-scale vortices have recently been found in the lower atmosphere of the quiet Sun in state-of-the-art solar observations and in numerical simulations.
Aims: We investigate the characteristics and temporal evolution of a granular-scale vortex and its associated upflows through the photosphere and chromosphere of a quie…
Light walls around sunspots observed by the Interface Region Imaging Spectrograph
Zhang, J.; Hou, Y. J.; Li, T. +1 more
Context. The Interface Region Imaging Spectrograph (IRIS) mission provides high-resolution observations of the chromosphere and transition region. Using these data, some authors have reported the new finding of light walls above sunspot light bridges.
Aims: We try to determine whether the light walls exist somewhere else in active regions in …
Flux rope proxies and fan-spine structures in active region NOAA 11897
Zhang, J.; Hou, Y. J.; Li, T.
Context. Flux ropes are composed of twisted magnetic fields and are closely connected with coronal mass ejections. The fan-spine magnetic topology is another type of complex magnetic fields. It has been reported by several authors, and is believed to be associated with null-point-type magnetic reconnection.
Aims: We try to determine the numbe…