S.J. González Manrique, C. Kuckein, A. Pastor Yabar, M. Collados, C. Denker, M. Verma, A. Diercke, P. Gömöry, H. Balthasar, M. Cubas Armas, A. Lagg, S.K. Solanki, and K.G. Strassmeier

The new generation of solar instruments provides better spectral, spatial, and temporal resolution, which is essential to investigate the physical processes that take place on the Sun. High-resolution observations often show double- or even multiple-component spectral profiles. This is particularly true for observations of the near-infrared He I 10830 Å triplet. These spectral lines provide information on the velocity and magnetic fine structure of the upper chromosphere. We present observations of an emerging flux region (EFR), including two small pores visible in the photosphere and an arch filament system (AFS) in the chromosphere. The data were taken on 2015 April 17 with the very fast spectroscopic mode (~1 min for a full scan of 180 steps) of the GREGOR Infrared Spectrograph (GRIS), one of the post-focus instruments of the 1.5-meter GREGOR solar telescope located at the Observatorio del Teide, Tenerife, Spain. Simultaneous spectroscopic observations were taken with the GREGOR Fabry-Pérot Interferometer (GFPI) of the photospheric Fe I 6302 Å line. On the island of La Palma, the Swedish Solar Telescope (SST) observed the same EFR using the CRisp Imaging Spectro-Polarimeter (CRISP), which recorded spectropolarimetric data in the photospheric Fe I 6173 Å and the chromospheric Ca II 8542 Å lines. The observed AFS connects the two opposite magnetic polarities of newly emerging flux. Supersonic downflows up to 100 km s$^{-1}$ were measured in the He I triplet, which occur near both footpoints of dark filaments, whereas loop tops rise with about 1.5–20 km s$^{-1}$. The aim of this work is to track locations of high velocities within the footpoints of the arch filaments down to the photosphere. A special question arises, if the plasma contained in chromospheric structures, which exhibits supersonic LOS downflows near the footpoints of the AFS even reaches the photosphere.

Christoph Kuckein, Manuel Collados, Carsten Denker, Sami K. Solanki, Peter Gömöry, Meetu Verma, Horst Balthasar, and Andrea Diercke

We aim to study the evolution of an arch filament system (AFS) and of its individual arch filaments to learn about the processes occurring in them. We observed the AFS at the GREGOR solar telescope on Tenerife at high cadence with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) in the He I 10830 Å spectral range. The He I triplet line profiles were fit with analytical functions to infer line-of-sight (LOS) velocities to follow the plasma motions within the AFS. We tracked the temporal evolution of an individual arch filament over its entire lifetime as seen with the He I 10830 Å triplet. The studied individual arch filament expands in height and extends in length (from 13” to 21”). The lifetime of this arch filament is about 30 min. About 11~min after the arch filament is seen in He I, the loop top starts to rise with an average LOS velocity of 6 kms-1. Only two minutes later, plasma drains down with supersonic velocities towards the footpoints reaching peaks up to 40 kms-1 in the chromosphere. The temporal evolution of He I 10830 Å profiles near the leading pore showed almost ubiquitous dual red components of the He I triplet, indicating strong downflows, along with material nearly at rest within the same resolution element during the whole observing time. We follow the arch filament as it carries plasma during its rise from the photosphere to the corona. The material then drains toward the photosphere, reaching supersonic velocities, along the legs of the arch filament. Our observational results support theoretical AFS models and will serve to improve future models. The consequences of observations such as AFS for EST will be deduced. Also recommendations about EST performance and its instrumentation will be presented.