Collaborative Research: SHINE: What is Causing the Deficit of High-Energy Solar Particles in Cycle 24?

合作研究：SHINE：是什么导致第 24 周期高能太阳能粒子的不足？

• 批准号: 1622391
• 负责人: Gang Li
• 金额: $ 15.6万
• 依托单位: University of Alabama in Huntsville
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-15 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1622391&HistoricalAwards=false
• 关键词: Collaborative; Research; SHINE; What; Causing

This 3-year collaborative SHINE project is aimed at exploring and modeling a key under-appreciated aspect of the shock acceleration mechanism of solar energetic particles (SEPs) in the heliosphere, namely the role of the proton seed population in initiating and amplifying the shock acceleration process. This is one of the most important mechanisms in solar and heliospheric physics. The project will also explore how the maximum energy of SEPs can be limited by pre-existing suprathermal seed-particle densities and by the strength and turbulence level of the interplanetary magnetic field, which has been gradually declining over the past several solar cycles. Knowledge of suprathermal seed particle densities can aid in forecasting the maximum intensity of SEP events and in forecasting all-clear periods, providing a valuable space-weather tool. The PATH acceleration and transport model to be employed during this project will be put online, where it can be used by students and researchers to model SEP spectra, time profiles, maximum energies, and composition. This research project is especially relevant to the Solar Probe Plus and Solar Orbiter missions. The project will also employ a student and involve an under-represented minority. This 3-year SHINE project aims to understand the behavior of our Sun, which has dramatically changed in the last decade. The solar wind ram pressure and the solar magnetic field strength fell to a historic low. While solar cycles 22 and 23 were active with large SEP events, solar cycle 24 brought significantly fewer large events. The difference is particularly striking at the high-energy part (tens of MeV/n and up). This change, which has far reaching implications, puzzles the scientific community. This SHINE project aims at identifying the cause of this deficit. The project teams suggest that the two main causes are the reduced IMF strength and associated turbulence level, and reduced density of suprathermal seed particles. They will use the PATH model to understand how the maximum particle energy depends on: (i) the seed population; (ii) the background magnetic field; (iii) the upstream turbulence level; and, (iv) the shock speed and compression ratio. The investigators will also look at how changes in the seed population from solar cycle 23 to solar cycle 24 affect the accelerated spectra. The project is directly relevant to the NSF's SHINE program, because it will provide important knowledge about the acceleration and transport of SEPs during solar eruptive events. Such knowledge is critical for accurate modeling and prediction of space weather conditions from the solar surface to the Earth and beyond. The research and EPO agenda of this project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.

这个为期三年的协作光泽项目旨在探索和建模在气压层中太阳能颗粒（SEP）的冲击加速度机制的关键欠佳的方面，即质子种子种群在启动和放大冲击加速度中的作用过程。 这是太阳能和地球物理学中最重要的机制之一。 该项目还将探讨如何通过预先存在的外种子颗粒密度以及行星际磁场的强度和湍流水平来限制SEP的最大能量，在过去的几个太阳能周期中，该磁场的强度和湍流水平逐渐下降。 对超颗粒颗粒密度的知识可以帮助预测SEP事件的最大强度和预测的全明确时期，从而提供有价值的空间天气工具。 该项目期间要采用的路径加速度和运输模型将在线上进行，学生和研究人员可以在其中使用它来建模SEP光谱，时间概况，最大能量和构图。 该研究项目与太阳能探针Plus和太阳能轨道仪任务特别相关。 该项目还将雇用一个学生，并涉及代表性不足的少数民族。 这个为期三年的Shine项目旨在了解我们的太阳的行为，在过去的十年中，这种行为发生了巨大变化。 太阳能风杆压力和太阳能磁场强度跌至历史悠久的低点。 尽管太阳能循环22和23具有大型SEP事件，而太阳周期24的大事件则大大减少了。 在高能部分（数十个MEV/N及以上），差异尤其引人注目。 这种变化具有很大的影响，使科学界感到困惑。 这个Shine项目旨在确定这种赤字的原因。 项目团队认为，这两个主要原因是IMF强度和相关的湍流水平降低，以及降低的外颗粒颗粒密度降低。 他们将使用路径模型来了解最大粒子能量如何依赖：（i）种子种群； （ii）背景磁场； （iii）上游湍流水平； （iv）冲击速度和压缩比。 研究人员还将研究种子种群从太阳周期23到太阳周期24的变化如何影响加速光谱。 该项目与NSF的Shine计划直接相关，因为它将在太阳喷发事件中提供有关SEP的加速和运输的重要知识。 这种知识对于从太阳能表面到地球及以后的太空天气条件进行准确的建模和预测至关重要。 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。