For the past year, all departments of KIS worked together to carry out the biggest change of GREGOR since its inauguration. By replacing the relay optics and rearranging the AO and the majority of the instruments in the optics lab, we were able to significantly improve GREGOR's image quality and prepare the telescope for future instrumentation upgrades.

Magnetic flux cancelation refers to the interaction of opposite polarity magnetic elements leading to magnetic flux removal from the solar surface. If the interacting elements are previously unconnected, their cancelation is treated as an observational signature of magnetic reconnection.

Using high-resolution data obtained with the GREGOR telescope on Tenerife, we witnessed such a magnetic field reconnection event. The Integral Field Unit (IFU, built by Instituto de Astrofísica de Canarias, IAC) of the GREGOR Infrared Spectrograph (GRIS) recorded the Stokes profiles in the photospheric Si i 10827Å spectral line targeting the quiet-Sun at disk center.

On Monday, February 10, 2020 at 5:03 a.m. (CET), the ESA satellite Solar Orbiter was successfully launched with an Atlas 5 rocket from the Cape Canaveral Air Force Station in Florida. In less than 2 years the satellite will reach an orbit around the sun, where it can start scientific observations.

On Nov 11, 2019 KIS scientists together with C. Schmidt from Boston University observed and recorded the Mercury transit in front of the Sun with the GREGOR and Chrotel telescopes. Mercury transits are rare events and the next one will occur only in 2032. Such transits are great opportunities to study Mercury's exosphere. The first two-dimensional image of this exosphere was obtained by H. Schleicher at KIS at the occasion of the second to last transit in 2003, using the VTT telescope and the spectral line of sodium.

Inversion codes for the radiative transfer equation are tools that allow us to determine the temperature, magnetic field and plasma velocity in the solar atmosphere from spectro-polarimetric observations (i.e. Stokes vector) in spectral lines as a function of the optical depth.

Polarimetry is a sensitive technique for detecting magnetic fields, atmospheres, surfaces, atoms, molecules and dust grains, in astronomical objects such as the Sun, other distant stars, solar and exo-planets, asteroids, nebulae, and even black holes. The new, high-precision astronomical imaging polarimeter DIPOL-UF (Double Image Polarimeter – Ultra Fast) has been built in cooperation between KIS and a research group from the University of Turku (UTU), Finland; see the UTU press release here: www.utu.fi/en/news/news/new-astro-polarimeter-sees-first-light-at-the-nordic-optical-telescope.

GREGOR is the largest European Solar Telescope and recent enhancements in optics have allowed us to observe the Sun in extremely high resolution. The images show two snapshots, taken in August 2018 and the size of the Earth for comparison.

The controller of the Fabry-Perot Etalon for the Visible Tunable Filter instrument (VTF) has reached the demanding requirements for the controller precision and speed. The distance of the 20 kg Etalon plates can now be adjusted within a few milliseconds to the precision of a medium size atom. This is an important milestone towards the realization of the VTF. The multi-level controller was developed at KIS and has been verified on the basis of a full-size model of the Etalon.

The Leibniz-Institute for Solar Physics (KIS) has released a beta version of the new data archive for the GREGOR Infrared Spectrograph (GRIS, Collados et al. 2012, see below). All GRIS data prior to 2018 are in open access and available here: sdc.leibniz-kis.de

The database contains more than 650 data sets recorded in the years between 2014 and 2017. Most of them are single raster scans recorded in spectropolarimetric mode in the 1.08µm and 1.56µm wavelength bands. Some of them are measurements in spectroscopic mode, time sequences capturing the evolution of solar features, sit and stare measurements or observation in other wavelength bands such as 2.2µm.

Currently, the user can access the archive via a web interface. Best performance is achieved using ‘Chrome’ Browser. The initial web page provides the possibility to query by various parameters such as date, wavelength, heliocentric angle, etc. The results are displayed as a list with some information and preview images. For each...

Internal gravity waves (IGWs) are buoyancy-driven waves common in the Earth’s atmosphere and oceans. IGWs have also been observed in the Sun’s atmosphere and are thought to play an important role in the overall dynamics of the solar atmosphere.