Magnetized Double-diffusive Convection in Stars

对流是热量通过流体的大量流动从一个区域传递到另一个区域的过程。它在地球的大气、海洋、地球内部的熔融区域和恒星内部都很重要。双扩散对流（DDC）是由流体中两个不同密度梯度驱动的对流，每个密度梯度具有不同的扩散速率。一个例子是在海洋中，热量和盐的梯度以不同的速率驱动对流。DDC可能在恒星内部发挥重要作用。这个团队将使用数值模拟来研究恒星中的DDC，重点是磁场对扩散的影响。作为项目的一部分，首席研究员将为学生提供建议。她还参与了每年运行或参加暑期研究生培训项目。作为该项目的一部分，她计划在天体物理学中开展一个以恒星混合为主题的Kavli暑期项目。研究小组将继续利用数值模拟来表征双扩散不稳定性的输运性质（主要是热和化学物质）的最新进展。他们将继续研究其他过程的影响，如旋转和剪切，并开始研究磁场的影响。磁场在恒星中很常见，但很少有人研究它们对其他不稳定性的影响（除了基本的线性稳定性计算）。这个小组已经证明，垂直磁场可以通过指向对流增加数量级的输运（与认为它会减少输运的线性工作相反），这对红巨星分支星和白矮星的混合有重要的影响。他们将确定在倾斜磁场中是否可能产生类似的效应，并研究半耦合磁场的相互作用，他们将表征指法和振荡DDC的发电机特性，有旋转和没有旋转。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Convection is the process by which heat is transferred by the bulk flow of fluid from one region to another. It is important in the Earth's atmosphere, in the oceans, in molten regions within the Earth, and inside stars. Double diffusive convection (DDC) occurs when convection is driven by two different density gradients in the fluid, each of which has a different rate of diffusion. An example is within the ocean, where heat and salt gradients drive convection at different rates. DDC could play an important role in stellar interiors. This team will study DDC in stars using numerical simulations, with an emphasis on the effect of magnetic fields on diffusion. The principal investigator will advise students as part of her project. She is also involved each year in running or participating in summer graduate training programs. As part of the project, she plans to run a Kavli Summer Program in Astrophysics on the topic of Mixing in Stars.The research team will continue its recent progress in characterizing the transport properties (for heat and chemical species primarily) of double-diffusive instabilities using numerical simulations. They will continue to investigate the effect of other processes, such as rotation and shear, and start to look into the effect of magnetic fields. Magnetic fields are very common in stars, but little work has been done to study their effect on other instabilities (beyond basic linear stability calculations). This group has shown that vertical magnetic fields can increase transport by fingering convection by orders of magnitude (contrary to linear work that had suggested it would decrease transport), with important consequences for mixing in red giant branch stars and white dwarfs. They will determine whether similar effects are possible for inclined fields and also study the interaction of magnetic fields with semiconvection, and they will characterize the dynamo properties of both fingering and oscillatory DDC, with and without rotation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.