Calibration and Analysis of Mount Wilson Magnetograms and Dopplergrams for the Years 1967 to 2013

太阳影响地球及其环境的现象范围很广，如飞机的辐射水平、航天器的大气阻力、远距离输电、管道充电和无线电通信（特别是在高纬度地区）等。强烈的太阳风暴会破坏全球通信并损坏航天器。这些影响在“严重空间天气事件的社会和经济影响委员会：一个研讨会，国家研究委员会（2008年）”中有详细介绍，并在“太阳和空间物理十年战略委员会（太阳物理）：国家研究委员会（2013年）”中有进一步讨论。最近的第24太阳活动周期强度相对较低，而即将到来的第25太阳活动周期开始缓慢。通过代用指示器恢复的宇宙射线记录表明，太阳活动周期会经历持续一个世纪或更长时间的强弱周期，这些周期被称为极大期和极小期。在过去的几十年里，在理解太阳磁周期的机制方面取得了相当大的进展。在此过程中，将模式输出（包括预测的周期变率）与观测到的太阳周期特征进行比较，是验证模式的重要步骤。这个为期3年的研究项目旨在通过对威尔逊山天文台（MWO）收集的独特磁图数据进行新的校准过程，将可用的太阳周期数量从4个增加到5个，从而提高它们的质量，供更广泛的太阳-日光层社区进一步使用。在海尔（ge Hale）和巴布科克（H.W. Babcock）的领导下，MWO率先发现并测量了太阳表面磁场。从1964年到1985年，在R.F. Howard的指导下，测量了可见的太阳圆盘磁场，并在磁带上进行了数字记录。该项目的PI R.K. Ulrich从1986年到2013年管理该项目。完整的数字记录跨越了46年，或大约4个太阳周期。1967年至1973年是太阳活动周期20的主要部分，没有其他常规的磁场测量方法。1973年4月，基特峰国家天文台开始了每日磁图观测计划，1975年5月，斯坦福太阳天文台开始了每日观测，现在的威尔科克斯太阳天文台（WSO）， 1995年天基系统的数据可用。除了来自MWO的数据，所有这些数据系列今天都在继续。在这个为期3年的项目中，PI将对MWO磁图和多普勒图系列进行新的校准，该校准将考虑仪器硬件、校准数据采集方法和软件简化方法的各种变化。对1967-1969年磁图的初步分析表明，标称校准过程中存在明显的不规则性。此外，所有磁图测量都依赖于复杂的谱线形成过程，因此上述每个系列的导出场都是不同的，并且在每个系列中，由于仪器和校准的变化，会出现跨跃。在较长一段时间内持续校准的磁图数据集对于交叉校准（和识别系统分类）在同一时期内与其他仪器进行的磁场测量非常重要。太阳表面磁图的使用是计算和预测日球层状况所必需的。在一些研究中已经注意到一个“开放磁场通量问题”，因此磁图观测的校准和解释已成为一个中心问题。本项目将在项目团队之前开展的工作的基础上解决这一问题。重新校准各个阶段的数据产品，包括最终的最佳结果，将被保留，并通过与斯坦福大学JSOC系统的一部分斯坦福日震学档案馆的合作，向社区和公众提供。项目团队将与更广泛的太阳能社区合作，将MWO磁图纳入ADAPT/WSA管道，从而产生预测的太阳风特性。该项目的研究和EPO议程支持AGS部门在发现、学习、多样性和跨学科研究方面的战略目标。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。

The Sun influences the Earth and its environment in a large range of phenomena, such as aircraft radiation levels, atmospheric drag on spacecraft, long-distance power transmission, pipeline charging and radio communication (especially at high latitudes), etc. Severe solar storms can disrupt global communications and damage spacecraft. These effects have been detailed in "Committee on the Societal and Economic Impacts of Severe Space Weather Events: A Workshop, National Research Council (2008)," and are further discussed in "Committee on a Decadal Strategy for Solar and Space Physics (Heliophysics): National Research Council (2013)." The most recent solar cycle 24 was of relatively low strength, and the upcoming cycle 25 is beginning slowly. Cosmic ray records, as recovered by proxy indicators, suggest that the solar cycle goes through long periods of strength and weakness lasting one or more centuries, which are called grand maxima and grand minima. In the past few decades, there has been considerable progress in understanding the mechanisms governing the Sun's magnetic cycle. In this process, comparisons between model output, including predicted cycle variability and the observed characteristics of the solar cycle, is an essential step in the validation of the models. This 3-year research project is aimed at increasing the number of available solar cycles from four to five by carrying out a new calibration process of the unique magnetogram data gathered by the Mount Wilson Observatory (MWO), thus improving their quality for further use by the broader solar-heliospheric community.The MWO, under the direction of G.E. Hale and H.W. Babcock, pioneered in the discovery and measurement of solar surface magnetic fields. From 1964 to 1985, under the direction of R.F. Howard, the visible solar disk magnetic fields were measured and digitally recorded on magnetic tape. The PI of this project, R.K. Ulrich, managed the program from 1986 to 2013. The full digital record spans 46 years, or about four solar cycles. For the years 1967 to 1973, a major part of solar cycle 20, no other set of regular magnetic field measurements is available. In April 1973 a program of daily magnetogram observations was started at the Kitt Peak National Observatory, and in May 1975 daily observations began at the Stanford Solar Observatory, now the Wilcox Solar Observatory (WSO), with data from space-based systems becoming available in 1995. All these data series, except that from the MWO, continue today. During this 3-year project, the PI will carry out a new calibration of the MWO magnetogram and Dopplergram series, which will take into account various changes in the instrument hardware, calibration data acquisition methods and software reduction methods. Initial analysis of the magnetograms from 1967-1969 shows that there are significant irregularities in the nominal calibration process. Also, all the magnetogram measurements depend on complex spectral line formation processes so that the derived fields are different for each of the series referenced above and, within each series, across jumps due to instrument and calibration changes. The resulting dataset of magnetograms consistently calibrated over an extended period of time is important for cross-calibrating (and identifying systematics in) the magnetic field measurements taken with other instruments during the same period of time. The use of solar surface magnetograms is required for the calculation and prediction of conditions in the heliosphere. An "Open Magnetic Field Flux Problem" has been noted in several studies, so that the calibration and interpretation of the magnetogram observations has become a central issue. This project will address this issue following up on the work carried out previously by the project team. The data products from various stages of the recalibration, including the final, best result will be retained and made available to the community and public through partnership with the Stanford Helioseismology Archive which is part of the JSOC system at Stanford University. The project team will work with the broader solar community to incorporate the MWO magnetograms into the ADAPT/WSA pipeline, which yields predicted properties of the solar wind. The research and EPO agenda of this project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.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.