Turbulence in Collisionless Astrophysical Plasmas

天体物理等离子体很少被观测到是静态的。相反，它们在时间和空间上都有很强的变化，这一现象被称为湍流。这类等离子体通常也具有磁场，就像地球和太阳一样。因此，需要了解磁化等离子体中的湍流(称为MHD湍流)，才能理解各种天体物理现象，从太阳系的太阳风(以及太阳风如何影响地球)到落入黑洞的气体旋转盘(黑洞产生一些宇宙中最明亮的光源)。我们的研究是为了了解MHD湍流在能量转化为热的小尺度上的行为，我们建议在小尺度上对MHD湍流的性质进行大规模的数值计算。这些计算将预测湍流的可观测特性，这些特性可以直接与太阳风的测量结果进行比较，并最终在地球上的实验室进行测量。同样的计算将预测当气流中包含的能量耗散时等离子体如何被加热--这是我们理解湍流的主要未解决问题之一。这些结果将与太阳风中的测量结果进行比较；它们也将被用来预测我们看到的落入黑洞的等离子体的光线--我们观察自然界中黑洞的主要窗口。更广泛地说，这里提出的计算将推进磁化等离子体中湍流数值模拟的最新水平，并将对各种实验室、空间和天体物理等离子体产生影响。

Astrophysical plasmas are rarely observed to be static. Instead theyvary strongly in both time and space, a phenomena known as turbulence.Such plasmas are also typically endowed with magnetic fields, justlike the Earth and the Sun. An understanding of turbulence inmagnetized plasmas (known as MHD turbulence) is thus required tounderstand a wide variety of astrophysical phenomena, from the solarwind in our solar system (and how the solar wind impacts Earth) torotating disks of gas falling into black holes (which produce some ofthe brightest sources of light in the Universe). Our proposedresearch is aimed at understanding the behavior of MHD turbulence onsmall scales where the energy is converted into heat.We propose to carry out large-scale numerical calculations of theproperties of MHD turbulence on small scales. These calculations willpredict observable properties of the turbulence that can be directlycompared to measurements in the solar wind, and ultimately tomeasurements in the laboratory on Earth. The same calculations willpredict how plasmas are heated when the energy contained in theturbulence is dissipated -- one of the major unsolved problems in ourunderstanding of turbulence. These results will be compared tomeasurements in the solar wind; they will also be used to predict thelight we see from plasma falling into black holes -- our primaryobservational window onto black holes in nature. More broadly, thecalculations proposed here will advance the state-of-the-art innumerical modeling of turbulence in magnetized plasmas and will haveimplications for a wide variety of laboratory, space, andastrophysical plasmas.