On the fine structure of the quiet solar \Ca II K atmosphere

Three independent sets of data: i). series of filtergrams obtained in line CaII K (393.416 nm) with the ground-based telescope Precision Solar Photometric Telescope (PSPT) of Mauna Loa Solar Observatory; ii). series of filtergrams of Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) in {\lambda}160 nm and iii). series of magnetograms of Helioseismic and Magnetic Imager (HMI) of SDO have been processed to reveal reliably the existence of spatial cellul...

The migration of magnetic bright point-like features (MBP) in the lower solar atmosphere reflects the dispersal of magnetic flux as well as the horizontal flows of the atmospheric layer they are embedded in. We analyse trajectories of the proper motion of intrinsically magnetic, isolated internetwork Ca II H MBPs (mean lifetime 461 +- 9 s) to obtain their diffusivity behaviour. We use seeing-free high spatial and temporal resolution image sequences of quiet-Sun, disc-centre o...

We present the initial results of an observational study into the variation of the dominant length-scale of quiet solar emission: supergranulation. This length-scale reflects the radiative energy in the plasma of the upper solar chromosphere and transition region at the magnetic network boundaries forming as a result of the relentless interaction of magnetic fields and convective motions of the Sun's interior. We demonstrate that a net difference of ~0.5Mm in the supergranula...

The Ca II infrared triplet is one of the few magnetically sensitive chromospheric lines available for ground-based observations. We present spectropolarimetric observations of the 8498 A and 8542 A lines in a quiet Sun region near a decaying active region and compare the results with a simulation of the lines in a high plasma-beta regime. Cluster analysis of Stokes V profile pairs shows that the two lines, despite arguably being formed fairly close, often do not have similar ...

The aim of this work is to study the structure of the magnetic field vector in the internetwork and search for the presence of small-scale loops. We invert 1.56 micron spectropolarimetric observations of internetwork regions at disc centre by applying the SIR code. This allows us to recover the atmospheric parameters that play a role in the formation of these spectral lines. We are mainly interested in the structure of the magnetic field vector. We find that many opposite pol...

We study the radiative emission of various types of solar features, such as quiet Sun, enhanced network, plage, and bright plage regions, identified on filtergrams taken in the Ca II K line. We analysed fulldisk images obtained with the PSPT, by using three interference filters that sample the Ca II K line with different bandpasses. We studied the dependence of the radiative emission of disk features on the filter bandpass. We also performed a NLTE spectral synthesis of the C...

We present the first high-resolution solar images in the Mg II k 2796 \AA{} line. The images, taken through a 4.8 \AA{} broad interference filter, were obtained during the second science flight of SUNRISE in June 2013 by the SuFI instrument. The Mg II k images display structures that look qualitatively very similar to images taken in the core of Ca II H. The Mg II images exhibit reversed granulation (or shock waves) in the internetwork regions of the quiet Sun, at intensity c...

The detection of Earth-like planets with the radial-velocity method is currently limited by the presence of stellar activity signatures. On rotational timescales, spots and plages (or faculae) are known to introduce different RV signals, but their corrections require better activity proxies. The best-known chromospheric activity proxies in the visible are the Ca II H & K lines, but the physical quantities measured by their profiles need to be clarified. We first investigate r...

High-resolution imaging observations from the Hinode spacecraft in the CaII H line are employed to study the dynamics of the chromosphere above a sunspot. We find that umbral flashes and other brightenings produced by the oscillation are extremely rich in fine structure, even beyond the resolving limit of our observations (0.22"). The umbra is tremendously dynamic, to the point that our time cadence of 20 s does not suffice to resolve the fast lateral (probably apparent) moti...

The magnetic network observed on the solar surface harbors a sizable fraction of the total quiet Sun flux. However, its origin and maintenance are not well known. Here we investigate the contribution of internetwork magnetic fields to the network flux. Internetwork fields permeate the interior of supergranular cells and show large emergence rates. We use long-duration sequences of magnetograms acquired by Hinode and an automatic feature tracking algorithm to follow the evolut...