Parallel Computing Resources for the UK MHD Community

实际上，宇宙中的所有物质都是由一种叫做等离子体的电离气体组成的。等离子体导电并与磁场相互作用，产生许多在地球实验室中不易重现的物理现象。这些等离子体的大规模行为可以通过一组已知的复杂数学方程来预测，这些方程被称为磁流体动力学方程（MHD）。MHD方程的解可以描述等离子体的行为，其中碰撞主导物理过程，例如(i)通过称为发电机作用的过程产生磁场，（ii）通过磁重联在大型太阳耀斑中释放惊人数量的磁能，（iii）磁化等离子体中湍流的小尺度混沌运动。（iv）太阳大气层比太阳表面热得多的事实和(v)太阳等离子体的巨大喷发与地球磁场相互作用产生极光的方式。当碰撞效应较弱时，在低密度等离子体和涉及短长度尺度的问题中，必须解决更基本的动力学方程。然而，这两组方程的解都需要非常大的计算机，最好的方法是将几百台计算机连接在一起，让它们都处理大问题的一小部分。这些计算机被称为并行计算机。英国在这一研究领域的努力处于世界范围内了解太阳、太阳系和天体物理等离子体如何工作的最前沿。虽然这项工作基本上是理论上的，但它是由现有的太阳和天体物理地面和空间天文台的观测结果驱动的。

Virtually all material in the universe consists of an ionised gas called a plasma. Plasmas conduct electricity and interact with magnetic fields, producing many physical phenomena not easily reproduced in laboratories on Earth. The large-scale behaviour of these plasmas can be predicted by using a known set of complicated mathematical equations, called the equations of Magnetohydrodynamics (MHD). The solutions of MHD equations can describe the behaviour of plasmas in which collisions dominate the physical processes, such as (i) the generation of magnetic fields through a process known as dynamo action, (ii) the release of a staggering amount of magnetic energy in a large solar flare by magnetic reconnection, (iii) the small scale chaotic motions of turbulence in a magnetised plasma, (iv) the fact that solar atmosphere is much hotter than the solar surface and (v) the way in which gigantic eruptions of solar plasma interact with the Earth's magnetic field to produce the Aurora. When collisional effects are weak, in low-density plasmas and in problems involving short length-scales, the more fundamental kinetic equations must be solved. However, the solution of both sets of equations require extremely large computers and the best way is to link several hundred computers together and get them all working on a fraction of the large problem. These computers are called parallel computers. The UK effort in this research area is at the forefront of the worldwide effort to understand how the Sun, the Solar System and astrophysical plasmas work. While this work is essentially theoretical, it is driven by the observations of the present fleet of solar and astrophysical ground and space-based observatories.