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

这个为期3年的合作SHINE项目旨在探索和模拟日光层中太阳高能粒子（SEP）的冲击加速机制的一个关键方面，即质子种子群在启动和放大冲击加速过程中的作用。 这是太阳和日光层物理学中最重要的机制之一。 该项目还将探索如何通过预先存在的超热种子粒子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，行星际磁场在过去几个太阳周期中逐渐下降。 超温种子粒子密度的知识可以帮助预测SEP事件的最大强度和预测完全清除期，提供了一个宝贵的空间气象工具。 在这个项目中使用的PATH加速和传输模型将被在线，学生和研究人员可以使用它来模拟SEP光谱，时间曲线，最大能量和成分。 该研究项目与太阳探测器和太阳轨道飞行器任务特别相关。 该项目还将雇用一名学生，并涉及代表性不足的少数民族。 这个为期3年的SHINE项目旨在了解太阳的行为，太阳在过去十年中发生了巨大的变化。 太阳风冲压压力和太阳磁场强度下降到历史最低点。 虽然太阳活动周期22和23是活跃的与大型SEP事件，太阳活动周期24带来了显着较少的大型事件。 这种差异在高能部分（数十MeV/n及以上）尤为明显。 这种影响深远的变化令科学界感到困惑。 这个SHINE项目的目的是确定这种赤字的原因。 项目小组认为，两个主要原因是IMF强度和相关湍流水平的降低，以及超热种子颗粒密度的降低。 他们将使用PATH模型来理解最大粒子能量如何取决于：（i）种子数量;（ii）背景磁场;（iii）上游湍流水平;以及（iv）激波速度和压缩比。 研究人员还将研究从太阳周期23到太阳周期24的种子数量变化如何影响加速光谱。 该项目与NSF的SHINE计划直接相关，因为它将提供有关太阳爆发事件期间SEP加速和运输的重要知识。 这类知识对于准确建模和预测从太阳表面到地球及其以外的空间气象条件至关重要。 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。

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.