RUI: Magnetic Diffusivity in a Predictive Solar Dynamo Model

RUI：预测太阳能发电机模型中的磁扩散率

• 批准号: 0807651
• 负责人: Elizabeth Zita
• 金额: $ 18.77万
• 依托单位: Evergreen State College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0807651&HistoricalAwards=false
• 关键词: RUI; Magnetic; Diffusivity; Predictive; Solar

Understanding the solar activity cycle remains one of the key problems in solar physics. Observed magnetic activities, such as sunspot cycles and magnetic field reversals, produce solar flares and coronal mass ejections, with significant influences on the Earth. Physicists generally believe that a magnetohydrodynamic dynamo produces the observed 11-year activity cycle by generating and changing magnetic fields in the solar convection zone (the outer 30% of the Sun). Progress has been made in solar dynamo theory to the point that computational models may now be used as predictive tools (to a certain extent). The solar dynamo depends on the shearing, buoyancy, twisting and flows of magnetic plasma, the hot ionized gas that makes up the Sun. One of the least understood aspects of the solar dynamo concerns a material property of the Sun itself - the magnetic diffusivity, which contributes to changes in magnetic fields, and is itself changed by dynamic magnetic fields. A more complete understanding of the magnetic diffusivity in the convection zone, and of its effects on the evolution of solar magnetic fields, is required to more fully understand the solar dynamo. This is not only an interesting theoretical problem in solar physics and magnetohydrodynamics, it is also of practical importance to technologies that are sensitive to solar activity (from communications satellites to power grids), and to understanding the impact of the variable Sun on our biosphere.Here, a proven solar dynamo model will be improved to better predict future solar cycles. The two dimensional, nonlinear, kinematic flux-transport dynamo model will be used to investigate the detailed causes and effects of diffusivity variations in radius, latitude, and time, due to factors such as temperature, turbulence, and changes in the local magnetic field strength. Dr. Zita will carry out investigations that will include important new physics such as dynamical magnetic quenching of diffusivity, and magnetic advection due to diffusivity gradients. Systematic evaluation of each effect, and comparison with other key dynamo elements, will deepen insight into the fundamental mechanisms of the solar dynamo. Her investigations will contribute directly to key goals in solar physics, including understanding how magnetic fields appear, distribute, and disappear from their origin in the solar interior; and quantification of the physics, dynamics, and behavior of the system over the solar cycle. The research will produce (1) physics-based diffusivity models for use by solar dynamo modelers and (2) an improved dynamo model for prediction of future solar cycles. This work can also illuminate dynamos in other stars, galaxies, and fusion plasmas; and mechanisms by which magnetic energy can be transformed into heat in the solar chromosphere and corona, as these all require better understanding of magnetic diffusivity. Undergraduates will be directly involved in the research at all stages. Ongoing scientific collaborations with the High Altitude Observatory at the National Center for Atmospheric Research will give students access to high quality research experiences. Dr. Zita is also active in public science literacy and science outreach to girls, and her home institution is a pioneer in outreach to students from underrepresented groups. Research projects such as the work supported here are routinely integrated into interdisciplinary college curricula. Finally, the project will strengthen the infrastructure for solar physics research, established in recent years at Evergreen College in the collaboration with the High Altitude Observatory.

了解太阳活动周期是太阳物理学的关键问题之一。观测到的磁活动，例如太阳黑子周期和磁场逆转，会产生太阳耀斑和日冕物质抛射，对地球产生重大影响。物理学家普遍认为，磁流体动力发电机通过产生和改变太阳对流区（太阳外部30%）的磁场来产生观测到的11年活动周期。太阳发电机理论已经取得了进展，计算模型现在可以用作预测工具（在一定程度上）。太阳发电机依赖于磁场等离子体的剪切、浮力、扭曲和流动，磁场等离子体是构成太阳的热电离气体。太阳能发电机最不为人所知的一个方面是太阳本身的一种物质属性--磁扩散率，它有助于磁场的变化，并且它本身也会被动态磁场所改变。为了更全面地了解太阳发电机，需要更全面地了解对流区的磁扩散率及其对太阳磁场演化的影响。这不仅是太阳物理学和磁流体力学中一个有趣的理论问题，而且对于对太阳活动敏感的技术（从通信卫星到电网）以及理解太阳变量对我们生物圈的影响也具有重要的实际意义。在这里，一个经过验证的太阳发电机模型将被改进，以更好地预测未来的太阳周期。二维的，非线性的，运动学通量输运发电机模型将被用来研究详细的原因和影响的扩散率变化的半径，纬度和时间，由于温度，湍流，和局部磁场强度的变化等因素。Zita博士将进行调查，其中包括重要的新物理学，如扩散率的动态磁淬火，以及由于扩散率梯度引起的磁平流。对每种效应进行系统评估，并与其他关键发电机元素进行比较，将加深对太阳发电机基本机制的了解。她的研究将直接有助于太阳物理学的关键目标，包括了解磁场如何出现，分布和从太阳内部的起源消失;以及在太阳周期内系统的物理，动力学和行为的量化。该研究将产生（1）基于物理学的扩散率模型，供太阳发电机建模者使用;（2）改进的发电机模型，用于预测未来的太阳周期。 这项工作也可以照亮发电机在其他恒星，星系，和融合等离子体;和机制，其中磁能可以转化为热量在太阳色球层和日冕，因为这些都需要更好地了解磁扩散率。本科生将直接参与研究的各个阶段。与国家大气研究中心的高海拔天文台正在进行的科学合作将使学生获得高质量的研究经验。Zita博士还积极参与对女孩的公共科学扫盲和科学宣传，她所在的机构是对代表性不足的群体的学生进行宣传的先驱。研究项目，如这里支持的工作通常被纳入跨学科的大学课程。最后，该项目将加强近年来在万年青学院与高海拔观测站合作建立的太阳物理学研究基础设施。