3 years ago

Effects of variable thermal diffusivity on the structure of convection.

O.V. Shcheritsa, A.V. Getling, O.S. Mazhorova

The multiscale flow structure in the solar convection zone - the coexistence of such features as the granules, mesogranules, supergranules and giant cells - has not yet been properly understood. Here, the possible role of one physical factor - variations in the thermal diffusivity - in the formation of a multiscale convection structure is investigated. Thermal convection in a plane horizontal fluid layer is numerically simulated. The temperature dependence of thermal diffusivity is chosen so as to produce a sharp kink in the static temperature profile near the upper layer boundary. As a result, the magnitude of the (negative) static temperature gradient dTs/dz, being small over the most part of the layer thickness, reaches large values in a thin boundary sublayer. To identify the structures on different scales, we apply a smoothing procedure, computational-homology techniques and spectral processing to the temperature field. The flow is found to be a superposition of three cellular structures with three different characteristic scales. The largest (first-scale) convection cells, with central upflows, fill the whole layer thickness; most of these cells are divided by bridges, or isthmuses, into a few smaller (second-scale) ones, which are localised in the upper portion of the layer; finally, there are numerous tiny (third-scale) features that dot the horizontal sections of the layer located near its upper boundary and exhibit a tendency of gathering in the intercellular lanes of the first-scale cells. The third-scale cellular structures are advected by the first-scale and second-scale convective flows. The spatial spectrum of the flow does not directly indicate the presence of the second-scale and third-scale structures; however, they can be selected by using our processing techniques. On the whole, the simulated flow pattern qualitatively resembles that observed on the Sun.

Publisher URL: http://arxiv.org/abs/1604.02543

DOI: arXiv:1604.02543v2

You might also like
Never Miss Important Research

Researcher is an app designed by academics, for academics. Create a personalised feed in two minutes.
Choose from over 15,000 academics journals covering ten research areas then let Researcher deliver you papers tailored to your interests each day.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.