Large-Eddy Simulations of Magnetohydrodynamic Turbulence in Heliophysics and Astrophysics

We live in an age in which high-performance computing is transforming the way we do science. Previously intractable problems are now becoming accessible by means of increasingly realistic numerical simulations. One of the most enduring and most challenging of these problems is turbulence. Yet, despite these advances, the extreme parameter regimes encountered in space physics and astrophysics (as in atmospheric and oceanic physics) still preclude direct numerical simulation. Numerical models must take a Large Eddy Simulation (LES) approach, explicitly computing only a fraction of the active dynamical scales. The success of such an approach hinges on how well the model can represent the subgrid-scales (SGS) that are not explicitly resolved. In addition to the parameter regime, heliophysical and astrophysical applications must also face an equally daunting challenge: magnetism. The presence of magnetic fields in a turbulent, electrically conducting fluid flow can dramatically alter the coupling between large and small scales, with potentially profound implications for LES/SGS modeling. In this review article, we summarize the state of the art in LES modeling of turbulent magnetohydrodynamic (MHD) ows. After discussing the nature of MHD turbulence and the small-scale processes that give rise to energy dissipation, plasma heating, and magnetic reconnection, we consider how these processes may best be captured within an LES/SGS framework. We then consider several special applications in heliophysics and astrophysics, assessing triumphs, challenges,and future directions

'So, you're from Brixton?': the struggle for recognition and esteem in a multicultural community

This article examines how the struggle for recognition and esteem permeates everyday experiences in the context of young people growing up in Brixton, south London, UK. It begins with a brief history of Brixton and an explanation of the qualitative methods (focus groups and interviews) and thematic analysis used in the research. The findings are then discussed in three sections. The first section illustrates how identity is constructed through and against the representations held by others within particular social contexts. Focusing on the varying strategies that different young people adopt in constructing a positive identity reveals the salience of racist representations in the social construction of Brixton. The second section examines the effects this can have on the self-image and self-esteem of many in the study, looking in particular at strategies used to contest negative versions of blackness. This points to the racializing and gendering within the (re)production of local youth identities. The concluding section illustrates how some young people collaboratively develop the social and psychological resources to protect themselves against the prejudices of others. Together, this material reveals how social relationships and institutional cultures empower/disempower Brixton's youth in their collaborative struggle for recognition and esteem. This allows us to consider how new multicultures address, incorporate and resist new racisms and prejudices towards a locality