Dynamics of small-scale convective motions

Previous studies have discovered a population of small granules with diameters less than 800 km showing differing physical properties. High resolution simulations and observations of the solar granulation, in combination with automated segmentation and tracking algorithms, allow us to study the evolution of the structural and physical properties of these granules and surrounding vortex motions with high temporal and spatial accuracy. We focus on the dynamics of granules (lifetime, fragmentation, size, position, intensity, vertical velocity) over time and the influence of strong vortex motions. Of special interest are the dynamics of small granules compared to regular-sized granules. We developed a temporal tracking algorithm based on our developed segmentation algorithm for solar granulation. This was applied to radiation hydrodynamics simulations and high resolution observations of the quiet Sun by SUNRISE/IMaX. The dynamics of small granules differ in regard to their diameter, intensity and depth evolution compared to regular granules. The tracked granules in the simulation and observations reveal similar dynamics (lifetime, evolution of size, vertical velocity and intensity). The fragmentation analysis shows that the majority of granules in simulations do not fragment, while the opposite was found in observations. Strong vortex motions were detected at the location of small granules. Regions of strong vertical vorticity show high intensities and downflow velocities, and live up to several minutes. The analysis of granules separated according to their diameter in different groups reveals strongly differing behaviors. The largest discrepancies can be found within the groups of small, medium-sized and large granules and have to be analyzed independently. The predominant location of vortex motions on and close to small granules indicates a strong influence on the dynamics of granules

Numerical Simulation of Coronal Waves interacting with Coronal Holes: I. Basic Features

We developed a new numerical code that is able to perform 2.5D simulations of a magnetohydrodynamic (MHD) wave propagation in the corona, and its interaction with a low density region, such as a coronal hole (CH). We show that the impact of the wave on the CH leads to different effects, such as reflection and transmission of the incoming wave, stationary features at the CH boundary, or formation of a density depletion. We present a comprehensive analysis of the morphology and kinematics of primary and secondary waves, that is, we describe in detail the temporal evolution of density, magnetic field, plasma flow velocity, phase speed and position of the wave amplitude. Effects like reflection, refraction and transmission of the wave strongly support the theory that large scale disturbances in the corona are fast MHD waves and build the major distinction to the competing pseudo-wave theory. The formation of stationary bright fronts was one of the main reasons for the development of pseudo-waves. Here we show that stationary bright fronts can be produced by the interactions of an MHD wave with a CH. We find secondary waves that are traversing through the CH and we show that one part of these traversing waves leaves the CH again, while another part is being reflected at the CH boundary inside the CH. We observe a density depletion that is moving in the opposite direction of the primary wave propagation. We show that the primary wave pushes the CH boundary to the right, caused by the wave front exerting dynamic pressure on the CH

Structure of the solar photosphere studied from the radiation hydrodynamics code ANTARES

The ANTARES radiation hydrodynamics code is capable of simulating the solar granulation in detail unequaled by direct observation. We introduce a state-of-the-art numerical tool to the solar physics community and demonstrate its applicability to model the solar granulation. The code is based on the weighted essentially non-oscillatory finite volume method and by its implementation of local mesh refinement is also capable of simulating turbulent fluids. While the ANTARES code already provides promising insights into small-scale dynamical processes occurring in the quiet-Sun photosphere, it will soon be capable of modeling the latter in the scope of radiation magnetohydrodynamics. In this first preliminary study we focus on the vertical photospheric stratification by examining a 3-D model photosphere with an evolution time much larger than the dynamical timescales of the solar granulation and of particular large horizontal extent corresponding to $25\!" \!\! \times \, 25\!"$ on the solar surface to smooth out horizontal spatial inhomogeneities separately for up- and downflows. The highly resolved Cartesian grid thereby covers $\sim 4~\mathrm{Mm}$ of the upper convection zone and the adjacent photosphere. Correlation analysis, both local and two-point, provides a suitable means to probe the photospheric structure and thereby to identify several layers of characteristic dynamics: The thermal convection zone is found to reach some ten kilometers above the solar surface, while convectively overshooting gas penetrates even higher into the low photosphere. An $\approx 145\,\mathrm{km}$ wide transition layer separates the convective from the oscillatory layers in the higher photosphere.Comment: Accepted for publication in Astrophysics and Space Science; 18 pages, 12 figures, 2 tables; typos correcte

e,e-trans-Cyclo­hexane-1,4-carb­oxy­lic acid–hexa­methyl­ene­tetra­mine (1/2)

The asymmetric unit of the title compound, 2C6H12N4·C8H12O4, contains one half-mol­ecule of e,e-trans-cyclo­hexane-1,4-dicarb­oxy­lic acid (the complete molecule being generated by inversion symmetry) and one mol­ecule of hexa­methyl­ene­tetra­mine (HMTA), which are connected by O—H⋯N hydrogen bonds. This forms isolated trimers that pack in a herringbone fashion

The hydrogen-bonding patterns of 3-phenylpropylammonium benzoate and 3-phenylpropylammonium 3-iodobenzoate: generation of chiral crystals from achiral molecules

The crystal structures and hydrogen-bonding patterns of 3-phenyl­propyl­ammonium benzoate, C9H14N+·C7H5O2-, (I), and 3-phenyl­propyl­ammonium 3-iodo­benzoate, C9H14N+·C7H4IO2-, (II), are reported and compared. The addition of the I atom on the anion in (II) produces a different hydrogen-bonding pattern to that of (I). In addition, the supra­molecular heterosynthon of (II) produces a chiral crystal packing not observed in (I). Compound (I) packs in a centrosymmetric fashion and forms achiral one-dimensional hydrogen-bonded columns through charge-assisted N-H...O hydrogen bonds. Compound (II) packs in a chiral space group and forms helical one-dimensional hydrogen-bonded columns with 21 symmetry, consisting of repeating R43(10) hydrogen-bonded rings that are commonly observed in ammonium carboxyl­ate salts con­tain­ing chiral mol­ecules. This hydrogen-bond pattern, which has been observed repeatedly in ammonium carboxyl­ate salts, thus provides a means of producing chiral crystal structures from achiral mol­ecules

Hydrogen Bonding Patterns in a Series of 3-Spirocyclic Oxindoles

The crystal structures of the new compounds spiro[cyclohexane-1,3’-indol] 2’(1’H)-one (1), (rel-1R,2S)-spiro[bicyclo[2.2.1] heptane-2,3’-indol] 2’(1’H)-one (2) and spiro[indole-3,2’-tricyclo[3.3.1.13,7]decan]-2(1H)-one (3) have been determined by low temperature single crystal X-ray diffraction. The effects of substitution on the hydrogen bonding pattern is compared between all three compounds.Keywords: Hydrogen Bonding, X-ray Crystal Structure, Oxindoles, Cambridge Structural Databas

A structural study of 4-aminoantipyrine and six of its Schiff base derivatives

Six derivatives of 4-amino-1,5-dimethyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-one (4-aminoantipyrine), C11H13N3O, (I), have been synthesized and structurally characterized to investigate the changes in the observed hydrogen-bonding motifs compared to the original 4-aminoantipyrine. The derivatives were synthesized from the reactions of 4-aminoantipyrine with various aldehyde-, ketone- and ester-containing molecules, producing (Z)-methyl 3-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]but-2-enoate, C16H19N3O3, (II), (Z)-ethyl 3-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]but-2-enoate, C17H21N3O3, (III), ethyl 2-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]cyclohex-1-enecarboxylate, C20H25N3O3, (IV), (Z)-ethyl 3-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]-3-phenylacrylate, C22H23N3O3, (V), 2-cyano-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamide, C14H14N4O2, (VI), and (E)-methyl 4-{[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]methyl}benzoate, C20H19N3O3, (VII). The asymmetric units of all these compounds have one molecule on a general position. The hydrogen bonding in (I) forms chains of molecules via intermolecular N-H⋯O hydrogen bonds around a crystallographic sixfold screw axis. In contrast, the formation of enamines for all derived compounds except (VII) favours the formation of a six-membered intramolecular N-H⋯O hydrogen-bonded ring in (II)-(V) and an intermolecular N-H⋯O hydrogen bond in (VI), whereas there is an intramolecular C-H⋯O hydrogen bond in the structure of imine (VII). All the reported compounds, except for (II), feature π-π interactions, while C-H⋯π interactions are observed in (II), C-H⋯O interactions are observed in (I), (III), (V) and (VI), and a C-O⋯π interaction is observed in (II).SP2016http://journals.iucr.org/c/issues/2015/02/00/fn3185

Cyclo­octanaminium hydrogen succinate monohydrate

In the title hydrated salt, C8H18N+·C4H5O4 −·H2O, the cyclo­octyl­ ring of the cation is disordered over two positions in a 0.833 (3):0.167 (3) ratio. The structure contains various O—H.·O and N—H⋯O inter­actions, forming a hydrogen-bonded layer of mol­ecules perpendicular to the c axis. In each layer, the ammonium cation hydrogen bonds to two hydrogen succinate anions and one water mol­ecule. Each hydrogen succinate anion hydrogen bonds to neighbouring anions, forming a chain of mol­ecules along the b axis. In addition, each hydrogen succinate anion hydrogen bonds to two water mol­ecules and the ammonium cation