Solar, stellar and planetary astrophysics in DAMTP

DAMTP 中的太阳、恒星和行星天体物理学

基本信息

批准号：
ST/J001570/1
负责人：
Gordon Ogilvie
金额：
$ 78.38万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FJ001570%2F1
关键词：
Solar stellar planetary astrophysics DAMTP

项目摘要

The Sun's magnetic field can be seen at the surface through the appearance of sunspots, which are also associated with solar flares and prominences. Sunspot activity is not constant, but waxes and wanes on an 11-year timescale. Disordered magnetic fields can be maintained by the turbulent motions of the plasma making up the outer part of the Sun, but the cyclical behaviour shows coherence between the two hemispheres and is clearly a global process operating throughout this convective zone. It is not clearly understood how the magnetic field organizes itself to produce such large-scale cyclical behaviour. A natural large-scale effect is provided by the internal rotation of the Sun, which varies rapidly near the base of the convection zone about two-thirds of the distance to the surface. Our work is devoted to producing a model of cyclical activity that draws its energy from this shearing motion and produces the rising magnetic field structures that eventually emerge as sunspots through the mechanism of magnetic buoyancy. Together with a simplified description of the effect of the convection, this model, which will be solved numerically, is expected to lead to a self-sustaining magnetic field with large-scale features that can be compared with solar behaviour.Discs of matter orbiting around a central mass are found in numerous astronomical settings, including protoplanetary discs of dusty gas surrounding young stars, where planets are formed, high-energy plasma accretion discs around black holes, and more familiar examples such as Saturn's rings and spiral galaxies. A great variety of planets and planetary systems continue to be discovered around other stars. We propose to investigate several aspects of the dynamics of astrophysical discs, the physics of planet formation and the dynamics of extrasolar planetary systems. We will study the properties of turbulence, magnetic fields and vortices in discs, and the behaviour of discs that are not circular and flat. We will investigate the tidal interaction between extrasolar planets and their host stars, which can strongly heat or even destroy the planets, and the interaction of planets and discs, which can greatly modify the size and shape of the planets' orbits. All this work is related to current observations.One of the outstanding problems in solar physics is to understand how the solar corona is heated. We know that the magnetic field plays a key role in transporting and transferring energy from beneath the solar surface into the solar atmosphere. This happens on many scales from nanoflares to microflares, major flares, prominence eruptions and coronal mass ejections. However, we do not yet fully understand how magnetic energy is converted into thermal and kinetic energy. Recent observations show that the solar atmosphere is highly dynamic; imaging instruments (SoHO/EIT, TRACE, Stereo, Hinode/XRT and more recently SDO/AIA) have provided spectacular high-spatial-resolution images and high-cadence movies. These suggest that equilibrium models may not be appropriate and non-equilibrium effects may need to be revisited, for example transient ionization and recombination and non-Maxwellian electron distributions.EUV (and X-ray) spectroscopy, combined with atomic physics calculations, is playing a major role in the field of solar physics. It is enabling the physical parameters of the plasma (temperature and electron density distributions, flows, elemental abundances and non-thermal broadening) to be determined and constraints to be placed on the various heating models. For the first time, we have spectroscopic observations from the SOHO, Hinode and SDO satellites detailed enough that we can directly compare observable quantities with those predicted by theoretical modelling, at least for coronal loops and flares. Also, for the first time, we can link the coronal properties with the evolution of the magnetic field as is observed in the photosphere while emerging.

太阳的磁场可以通过黑子的外观在表面上看到，这也与太阳耀斑和突出相关。黑子活动不是恒定的，而是在11年的时间尺度上蜡和减弱。磁场无序的磁场可以通过组成太阳外部的血浆的湍流运动来维持，但是周期性的行为表现出两个半球之间的连贯性，并且显然是整个对流区域运行的全球过程。尚不清楚磁场如何组织自己产生如此大规模的周期性行为。太阳的内部旋转提供了自然的大规模效应，太阳的内部旋转在对流区的底部附近迅速变化，约占距表面距离的三分之二。我们的工作致力于产生一个周期性活动模型，该模型从这种剪切运动中汲取了能量，并产生了上升的磁场结构，这些结构最终通过磁性浮力机理而最终作为日光浴物出现。再加上对流效应的简化描述，该模型将在数值上解决，预计将导致一个自我维持的磁场，具有大规模的特征，可以与太阳能行为进行比较。绕中央质量绕的物质散布在许多天文学的环境中发现了众多天文学环境，包括围绕着尘埃的年轻星星，构成了尘埃式的，构成了尘埃式的，构成了尘埃，构成了烟气，构成了烟气，构成了烟气，构成了浓度的，构成了烟气，构成了烟气，构成了烟气，构成了蛋白质，构成了烟气，这是构成的，构成了烟气，构成了烟气，这是构成的，构成了烟气，构成了烟气。孔，以及更熟悉的例子，例如土星的戒指和螺旋星系。在其他恒星周围继续发现各种各样的行星和行星系统。我们建议研究天体物理椎间盘动力学的几个方面，行星形成的物理学和极性行星外系统的动力学。我们将研究圆盘中湍流，磁场和涡旋的特性，以及不圆形和平坦的光盘的行为。我们将研究可强烈加热甚至破坏行星的潮汐相互作用，以及行星和圆盘的相互作用，这些行星和圆盘的相互作用可以大大改变行星轨道的大小和形状。所有这些工作都与当前的观察有关。太阳能物理学中的杰出问题之一是了解太阳能电晕的加热。我们知道，磁场在从太阳能表面下方运输和转移能量到太阳大气中起着关键作用。这发生在从纳米流量到微丝，主要耀斑，突出喷发和冠状质量弹出的许多尺度上。但是，我们尚未完全了解磁能如何转化为热和动能。最近的观察表明，太阳大气是高度动态的。成像仪器（SOHO/EIT，TRACE，Stereo，Hinode/XRT以及最近的SDO/AIA）提供了壮观的高空间分辨率图像和高环境电影。这些表明平衡模型可能不合适，可能需要重新审视非平衡效应，例如瞬时电离和重组以及非Maxwellian电子分布。EUV（and X射线）光谱与原子物理学计算相结合，在Solar Althicics领域中起了主要作用。它可以确定等离子体的物理参数（温度和电子密度分布，流量，元素丰度和非热拓宽），并将其放置在各种加热模型上。我们第一次从SOHO，HINODE和SDO卫星中进行了光谱观测，以至于我们可以将可观察的数量与理论建模预测的数量直接进行比较，至少对于冠状环和耀斑。同样，我们第一次可以将冠状特性与磁场的演化联系起来，如在崭露头角时在光球中观察到的。