MRI RI-Track 2: Development of the Expanded Owens Valley Solar Array (EOVSA)-15--Major Upgrade of a Community Facility for Solar and Space Weather Physics

扩展的欧文斯山谷太阳能阵列(EOVSA)目前由13个2.1米天线组成，工作在1-18 GHz频率范围，是世界上首屈一指的太阳能专用无线电阵列，配备了宽带微波成像光谱学。EOVSA由新泽西理工学院运营，自2021年以来一直作为NSF大气和地球空间科学部(AGS)地球空间设施计划下的社区设施得到支持。EOVSA涉及的科学几乎涵盖了太阳现象的方方面面，包括太阳耀斑的非热辐射和粒子加速、太阳活动区的热辐射、太阳喷发事件以及空间气象研究的几个方面。该项目是对EOVSA现有能力的重大升级。这次重大升级所产生的研究成果和数据产品将大大改善有关太阳活动的基本知识，并提供具有广泛社会影响的改进的空间气象数据产品。图像质量的改善将使数据更容易为普通用户和公众所访问。这种基于大学的仪器的研究被很好地整合到教育和培训中，学生和职业生涯早期的研究人员主要参与仪器的构建和操作、数据分析、理论开发和建模。EOVSA的主要目标是基础研究和发现，通过对从1-18 GHz到1 S的快速、连续的400 GHz频率的完整太阳进行快速、连续的多频率成像，增加我们对这一广泛的太阳现象的认识和理解。除了这项基础研究外，该仪器还产生了各种具有业务意义的日常数据产品，如F10.7图像、射电爆发图像、光谱和光曲线，用于监测和预报空间天气事件的应用研究。此次MRI将通过以下几个方面提升EOVSA的能力：(1)通过将EOVSA转换为统一阵列并为每个天线配备下一代宽带馈电喇叭来提高其极化测量能力，以实现宽带成像光谱偏振测量的全新能力。(2)通过在阵列中增加两个新的天线来提高其宽带成像性能。这一增加与现有的相关器基础设施完全兼容，将极大地提高图像质量，从而提高所有频率的光谱精度。观测到的射电辐射的偏振为太阳日冕磁场的方向提供了关键的诊断。新的偏振能力将使许多可能的应用成为可能，包括a)为测量太阳耀斑中快速演变的磁场的方向开辟一个新的窗口，以及b)对经常发生主要耀斑和爆发的太阳活动区的日冕磁场强度和拓扑结构施加更严格的限制。升级后的U-V覆盖范围增加了35%，从而使点扩散函数更加清晰，从而使图像和空间分辨率光谱的保真度大大提高，可用于定量分析。最后，升级后的阵列将纠正当前阵列的限制，实现全容量天空覆盖增加25%。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Expanded Owens Valley Solar Array (EOVSA), currently consisting of thirteen 2.1-m antennas operating in the 1-18 GHz frequency range, is the world’s premier solar-dedicated radio array equipped for broadband microwave imaging spectroscopy. The EOVSA, operated by the New Jersey Institute of Technology, has been supported as a community facility under the Geospace Facilities program of the NSF Division of Atmospheric and Geospace Sciences (AGS) since 2021. The science addressed by EOVSA covers nearly every aspect of solar phenomena, including nonthermal emission and particle acceleration from solar flares, thermal emission from solar active regions, solar eruptive events, and several aspects of space weather research. This project is a major upgrade of the existing capabilities of EOVSA. The research results and data products produced by this major upgrade will measurably improve basic knowledge of solar activity and provide improved space weather data products of broad societal impact. The improvements in the image quality will make the data more accessible to general users and the public. Research with this university-based instrument is well-integrated into education and training, where students and early-career researchers have major involvement in instrument construction and operation, data analysis, theory development, and modeling. The primary goal of EOVSA is basic research and discovery, to increase our knowledge and understanding of this wide range of solar phenomena through rapid, continuous multi-frequency imaging of the full Sun at 400 frequencies from 1–18 GHz with a rapid time cadence of 1 s. In addition to this fundamental research, the instrument produces a variety of daily data products of operational interest, such as F10.7 images, radio burst images, spectra, and light curves, for applied research in monitoring and forecasting space weather events. This MRI will upgrade EOVSA’s capabilities by: (1) Improving its polarization measurement capabilities by transforming EOVSA into a uniform array and equipping each antenna with next-generation wide-band feed horns, to enable the entirely new capability of broadband imaging spectropolarimetry. (2) Improving its broadband imaging performance by adding two new antennas to the array. This addition, which is fully compatible with the existing correlator infrastructure, will greatly enhance the image quality, and hence spectral precision at all frequencies. The polarization of the observed radio emission provides crucial diagnostics for the direction of the solar coronal magnetic field. The new polarization capabilities will enable many possible applications including a) opening up a new window for measuring the direction of the rapidly evolving magnetic field in solar flares, and b) placing much tighter constraints on the coronal magnetic field strength and topology in solar active regions where major flares and eruptions frequently occur. The 35% increase in u-v coverage from the upgrade leads to a much cleaner point spread function, resulting in images and spatially resolved spectra with vastly improved fidelity for quantitative analysis. Lastly, the upgraded array will correct a limitation of the current array to achieve a 25% increase in sky coverage with full capacity.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.