Solar Chromospheric Plasma Turbulence and Heating Driven by Neutral-Plasma Coupling

到达地球的大部分光都来自太阳的“表面”，一个被称为光球层的区域。太阳的色球层和日冕是太阳表面上方的区域，产生了大部分危险的紫外线和x射线辐射。这些区域还产生太阳风，一种带电粒子流，一种等离子体，以超过400公里/秒的速度到达地球。快速变化的辐射和太阳风都会产生太空天气，对航天器和宇航员造成危害，并通过诱导电流浪涌和中断通信对地球产生许多重要影响。一个长期存在的谜团阻碍了科学家对太阳大气的理解和准确建模：在光球层上方很短的距离上，色球层的温度几乎上升了两倍，为创造更热的日冕和太阳风提供了一些能量。该项目将研究以前未被探索的太阳色球层的物理过程，并对加热的起源提出更完整的基于物理的解释。这个项目将检验从光球中产生的中性太阳流体能否将足够的能量转移到等离子体湍流中，从而加热色球，从而解释观测到的紫外光谱。这需要五个相关的研究任务：(1)解决等离子体漂移和磁场，当一个对流的中性气体推动它穿过磁力线；(2)分析了该碰撞等离子体的流不稳定性理论；(3)进行一系列动力学模拟，以探索产生的湍流的非线性和热性质；(4)将产生的电子加热纳入辐射输运代码，以评估其对色球辐射的影响；(5)将预测结果与观测结果进行比较。这项资助将为招收和培训等离子体和太阳物理、模拟和建模方面的学生研究人员提供机会。这项研究，复杂的模拟器，以及这些学生的影响将远远超出这项资助的持续时间。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。

Most of the light reaching Earth originates at the "surface" of the sun, a region called the photosphere. The regions immediately above this surface, the solar chromosphere and corona, create most of the dangerous Ultraviolet (UV) and X-ray radiation. These regions also generate the solar wind, a stream of charged particles, a plasma, that reach the Earth at speeds in excess of 400km/s. Both the rapidly changing radiation and the solar wind create space weather that results in hazards for spacecraft, astronauts, and also have a number of important impacts on Earth by inducing current surges and disrupting communication. A long-standing mystery has prevented scientists from understanding and accurately modeling the solar atmosphere: a short distance above the photosphere, the chromosphere's temperature jumps up by almost a factor of two, providing some of the energy that creates the even hotter corona and solar wind. This project will investigate previously unexplored physical processes in the solar chromosphere and develop a more complete physics-based explanation of the origin of the heating. This project will examine whether neutral solar fluid flows, emerging from the photosphere, can transfer sufficient energy into plasma turbulence to heat the chromosphere in order to account for the observed UV spectra. This requires five linked research tasks: (1) solving for plasma drifts and fields when a convecting neutral gas pushes it across magnetic field lines; (2) analyzing the theory of streaming instabilities applicable to the collisional plasma found there; (3) performing a series of kinetic simulations to explore the nonlinear and thermal properties of the resulting turbulence; (4) incorporating the resulting electron heating into a radiative transport code in order to evaluate its impact on chromospheric radiance; and (5) comparing the resulting predictions with observations. This grant will provide opportunities to recruit and train student researchers in plasma and solar physics, simulations, and modeling. This research, the sophisticated simulators, and these students will have an impact far beyond the duration of this grant.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.