The Origin and Properties of Magnetic Dynamos Across the Sub-Stellar Boundary

这个项目是一项从射电到X射线波长的系统研究，研究超冷矮星中磁发电机的起源和性质。这些是低质量、未演化的恒星和亚恒星天体，它们弥合了恒星与行星之间的鸿沟，在数量上主导着银河系恒星的数量。超冷矮星具有完全对流的内部，长期以来一直被认为是磁性不活跃的。然而，最近对这些天体的研究发现了出人意料的强烈磁性活动。利用扩展的甚大阵列的灵敏度和带宽的提高，一种新的对60,000斯隆数字天空勘测超冷矮星的时间分辨光谱学的实施，以及对磁等离子体加热和粒子加速的同时观测，该项目将解决基本的悬而未决的问题：(一)磁场强度的分布；(二)磁场的规模、几何形状和相干时间尺度；以及(三)发电机机制的效率与诸如旋转、年龄或二元性等性质之间是否存在关联。本科生和研究生将获得电磁光谱数据的获取、分析和发布的经验，以及在低质量恒星、棕矮星、太阳系外行星和恒星磁场领域的专业知识。该项目还将把这一经验融入本科教育，并通过学生积极参与使用哈佛-史密森望远镜观察，缩小课堂学习和实践研究之间的差距。

This project is a systematic study, from radio to X-ray wavelengths, of the origin and properties of magnetic dynamos in ultracool dwarf stars. These are low-mass, unevolved stars and sub-stellar objects that bridge the star-planet gap and dominate the Galactic stellar population by number. Ultracool dwarfs have fully convective interiors and were long assumed to be magnetically inactive. However, recent studies of these objects uncovered unexpectedly vigorous magnetic activity. Taking advantage of the increase in sensitivity and bandwidth of the Expanded Very Large Array, a new implementation of time-resolved spectroscopy for 60,000 Sloan Digital Sky Survey ultracool dwarfs, and simultaneous observations of magnetic plasma heating and particle acceleration, the project will address fundamental open questions: (i) the distribution of magnetic field strengths; (ii) the scale, geometry, and coherence timescale of the magnetic fields; and (iii) whether there is a correlation between the dynamo mechanism efficiency and properties such as rotation, age, or binarity. Undergraduate and graduate students will gain experience with the acquisition, analysis, and publication of data across the electromagnetic spectrum, as well as expertise in the areas of low mass stars, brown dwarfs, extrasolar planets, and stellar magnetic fields. The project will also integrate this experience into undergraduate education, and narrow the gap between classroom learning and hands-on research, through the active participation of students in observing with Harvard-Smithsonian telescopes.