The EST Team

EST will be the largest solar telescope ever built in Europe. With a 4-metre primary mirror and state-of-the-art technology, it will furnish astronomers with a unique tool to understand the Sun. The main goal of EST is to investigate the structure, dynamics, and energetics of the lower solar atmosphere, where magnetic fields continually interact with the plasma, and magnetic energy is sometimes released in powerful explosions. Understanding these phenomena requires observing fundamental processes at scales of about 30 kilometres on the solar surface and short time scales. To accomplish this goal, EST will be equipped with the most advanced adaptive optics system and a suite of innovative instruments for high-resolution, high-sensitivity, multi-wavelength spectropolarimetric observations. The EST consortium successfully accomplished in 2011 the EST conceptual design, based on novel approaches thanks to the expertise accumulated by the EST partners in building powerful solar telescopes and instruments during the last decades. The inclusion of EST in the ESFRI roadmap in March 2016 represented a key milestone for the project, since it was recognised as a strategic European infrastructure that is expected to be ready for operations in about ten years from now. All these elements have led to the start of the Preparatory Phase of the project as an intermediate phase to consolidate its science goals, technical definition, legal issues and national budget contributions. In this talk, the most relevant aspects related to the present status of EST will be presented: main innovative technical characteristics, timeline, budget, preparatory phase, location of the facility, future legal entity for its construction and operation, as well as the expected involvement of the different European countries.

Integral field units (IFUs) represent the most important instrumental development for solar telescopes in recent times. They aim at obtaining the simultaneous spectral/spectropolarimetric information in all points in a 2D field of view at the best achievable spatial resolution. Present IFU developments are based on three different approaches: image slicers, microlenses, and optical fibres. The first two options have been addressed under the EST framework and very promising results have been obtained up to now. Fibre-based IFUs are being developed for one of the first-light instruments of DKIST. In this talk, the three alternatives will be presented and described, putting especial emphasis on the alternatives developed as prototypes of the future EST instruments. A microlens-based IFU has been developed by MPS and tested at the SST. In parallel, a slicer-based IFU has also been developed by IAC and tested at GREGOR. The latter has been offered to all observers at this telescope to gain experience about its performance, stability and data reduction and analysis. These prototypes are fundamental for the final definition of the EST spectrograph(s) and crucial for the science that will be addressable with EST. IFUs will facilitate, v.g., the study of the fast evolution of small-scale solar structures, high-frequency waves, fast acceleration and heating of the plasma, reconnection events, etc. The present status of these instrument developments will be presented, as well as the future steps for their improvement and their final expected performance if/when installed at EST.

E. Khomenko

The aim of this work is to measure possible differences in the dynamics of the ionized and neutral components of the solar plasma, as a manifestation of partial ionization effects due to an incomplete collisional coupling, causing deviations from ideal MHD. Here we report the detection of differences in ion and neutral velocities in prominences using very high temporal resolution spectral data obtained in 2012 at the German VTT (Observatorio del Teide, Tenerife). A time series of scans of a small portion of a solar prominence was obtained simultaneously with a high cadence using spectral lines of two elements with different ionization states, namely the CaII 8542 A and the HeI 10830 A. Displacements, widths and amplitudes of both lines were carefully compared to extract dynamical information about the plasma. Many dynamical features are detected, such as counterstreaming flows, jets and propagating waves. In all the cases we find a very strong correlation between the parameters extracted from the lines of both elements, confirming that both trace the same plasma. Nevertheless, we also find short-lived transients where this correlation is lost. These transients are associated with ion-neutral drift velocities of the order of several hundred m/s. The patches of non-zero drift velocity show coherence on time-distance diagrams. We continue and expand this initial study with another set of data, also obtained under similar conditions at the VTT in 2016, this time including He I D3 5876 A, Halpha, and Ca II 8542 A, measured simultaneously. The new dataset has an advantage of including two lines of neutral elements with different atomic mass, together with one line of an ionized element. The importance of such kind of simultaneous observations for detecting partial ionization effects will be emphasized. The EST instrumentation should be designed to make possible these type of observations with the highest temporal cadence and spatial resolution.

The tasks, deliverables and milestones related to Solarnet WP6 (Advanced Instrumentation Development) are described