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

Short-lived (100s or less), sub-arcsec to a couple of arcsec size features of enhanced brightenings in the narrowband images at the $\mathrm{H_{2V}}$ and $\mathrm{K_{2V}}$ positions of the Ca II H and K lines in the quiet Sun are known as bright grains. With simultaneous observations of a quiet Sun internetwork region in the Fe I 6173 {\AA}, Ca II 8542 {AA}, and Ca II K lines acquired by the CRisp Imaging Spectro-Polarimeter and the CHROMospheric Imaging Spectrometer instru...

It is well established that both total and spectral solar irradiance are modulated by variable magnetic activity on the solar surface. However, there is still disagreement about the contribution of individual solar features for changes in the solar output, in particular over decadal time scales. Ionized Ca II K line spectroheliograms are one of the major resources for these long-term trend studies, mainly because such measurements have been available now for more than 100 yea...

Generally it has been considered that the plages and sunspots are the main contributors to the solar irradiance. There are small scale structures on the sun with intermediate magnetic fields that could also contribute to the solar irradiance. It has not yet been quantified how much of these small scale structures contribute to the solar irradiance and how much it varies over the solar cycle. In this paper, we used Ca II K images obtained from the telescope installed at Koda...

We study chromospheric emission to understand the temperature stratification in the solar chromosphere. We observed the intensity profile of the CaIIH line in a quiet Sun region close to the disk center at the German Vacuum Tower Telescope. We analyze over 10^5 line profiles from inter-network regions. For comparison with the observed profiles, we synthesize spectra for a variety of model atmospheres with a non local thermodynamic equilibrium (NLTE) radiative transfer code. A...

Various aspects of the magnetism of the quiet sun are reviewed. The suggestion that a small scale dynamo acting at granular scales generates what we call the quiet sun fields is studied in some detail. Although dynamo action has been proved numerically, it is argued that current simulations are still far from achieving the complexity that might be present on the Sun. We based this statement not so much on the low magnetic Reynolds numbers used in the simulations but, above al...

We investigate the relationship between the photospheric magnetic field of small-scale magnetic elements in the quiet Sun (QS) at disc centre, and the brightness at 214 nm, 300 nm, 313 nm, 388 nm, 397 nm, and at 525.02 nm. To this end we analysed spectropolarimetric and imaging time series acquired simultaneously by the IMaX magnetograph and the SuFI filter imager on-board the balloon-borne observatory Sunrise during its first science flight in 2009, with high spatial and tem...

We present findings from an analysis of the fractal dimension of solar supergranulation as a function of latitude, supergranular cell size and solar rotation, employing spectroheliographic data in the Ca II K line of solar cycle no. 23. We find that the fractal dimension tends to decrease from about 1.37 at the equator to about 1 at 20 degree latitude in either hemisphere, suggesting that solar rotation rate has the effect of augmenting the irregularity of supergranular bound...

Broad-band images of the solar chromosphere in the Ca II H&K line cores around active regions are covered with fine bright elongated structures called bright fibrils. The mechanisms that form these structures and cause them to appear bright are still unknown. We aim to investigate the physical properties, such as temperature, line-of-sight velocity, and microturbulence, in the atmosphere that produces bright fibrils and to compare those to the properties of their surrounding ...

We investigate features that are observed in Ca ii H sequences from Hinode in places where reversed granulation seems to interact with p-modes. These features appear ubiquitously in the quiet sun. They are co-spatial with reversed granulation, and display similar general properties, but have sharper edges and show fast brightness changes. They also appear predominantly above wide intergranular lanes, indicating a potential connection with magnetism. We report on the appearanc...

We analyze a time sequence of Inter-Network (IN) magnetograms observed at the solar disk center. Speckle reconstruction techniques provide a good spatial resolution (0.5" cutoff frequency) yet maintaining a fair sensitivity (some 20G). Patches with signal above noise cover 60% of the observed area, most of which corresponds to intergranular lanes. The large surface covered by signal renders a mean unsigned magnetic flux density between 17G and 21G (1G \equiv 1Mx cm$^{-2}$). T...