Numerical MHD Simulations of Solar Magnetoconvection and Oscillations in Inclined Magnetic Field Regions

The sunspot penumbra is a transition zone between the strong vertical magnetic field area (sunspot umbra) and the quiet Sun. The penumbra has a fine filamentary structure that is characterized by magnetic field lines inclined toward the surface. Numerical simulations of solar convection in inclined magnetic field regions have provided an explanation of the filamentary structure and the Evershed outflow in the penumbra. In this paper, we use radiative MHD simulations to investigate the influence of the magnetic field inclination on the power spectrum of vertical velocity oscillations. The results reveal a strong shift of the resonance mode peaks to higher frequencies in the case of a highly inclined magnetic field. The frequency shift for the inclined field is significantly greater than that in vertical field regions of similar strength. This is consistent with the behavior of fast MHD waves.Comment: 9 pages, 6 figures, Solar Physics (in press

Modeling the Subsurface Structure of Sunspots

While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this paper, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out an helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by \citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic

Effects of carbohydrase-inhibiting compounds on in vitro rumen fermentation

Batch culture fermentations with ruminal content were conducted to determine the effects of plant-derived [bilberry extract (BBE), phaseolamin, white mulberry (WMB), common flax] carbohydrase-inhibiting compounds on microbial fermentation. The cultures with these compounds, at two different doses (15 and 150 mg), were compared with both acarbose (ACB) and batch cultures without the addition of any enzyme-inhibiting compounds (Control). Incubations were conducted in triplicate and replicated. The pH, volatile fatty acids, ammonia N, apparent dry matter (DMD) and starch disappearance were measured after 5 and 24 h of incubation. Treatment with ACB, after 5 h, significantly reduced maize meal fermentation, resulting in the highest pH levels (P<0.01), the lowest total VFA concentration (P=0.01) and the lowest DMD (P<0.01). On the opposite, BBE and WMB caused the highest drop in pH, due to the rapid fermentation of their sugar content. Treatment with BBE resulted in an increase in propionate and in an apparently low ammonia N concentration, whilst ACB (150 mg) led to the highest values of acetate (P<0.05) and to a relative high concentration of ammonia N. After 24 h the differences in the fermentation pattern among supplements remained similar to those found after 5 h. In addition, BBE showed an activity against starch degradation, although this effect was concealed by the fermentation of sugars present in that supplement. These results show that some compounds modify the fermentation pattern of the substrate, but further studies are needed to clarify their impact on the complex rumen microbial community