M-I Coupling: Physics Based Algorithm for the High Latitude Conductance and Its Implications

本研究的目的是开发一个基于物理的电离层电导率模块，该模块包含由电离层强对流电场驱动的电射流不稳定引起的异常加热。可靠的动态电离层电导和能量耗散模型覆盖整个太阳风输入范围，是构建全球电离层-磁层电动力学模型的关键要素，如地球空间环流模型（GGCM）、全球电离层模型（GIM）和TIME-GCM模型。此外，它们在全球磁流体动力学代码中电离层边界的表示中至关重要。LFM模型采用了基于简单处方的半经验模型，而同化模型——电离层电动力学同化映射（AMIE）是纳入GGCM的首选模型。模拟和实测数据对比表明，上述模型在局部电离层电场中等（20 mV/m）条件下具有良好的性能。在20 mV/m的局部电离层强电场作用下，电子霍尔电流引起的能量耗散机制变得重要。这一过程不包括在传统的电离层电动力学能量收支中，因为电流和电场彼此正交。因此耗散是异常的，并归因于众所周知的和实验记录的法利-布曼双流电喷射不稳定性。EISCAT雷达和更早的Chatanika雷达在e区高度观测到超过2000k的电子温度。这一过程除了起到非欧姆耗散的作用外，还通过改变电子复合系数，从而增加等离子体密度，从而导致Pederson和Hall电导的变化。在本研究中，将开发适当的算法，以便将其纳入AMIE、GIM、TIME-GCM和全球MHD代码。新的传导模块将分发给更广泛的空间科学界，以评估其表示观测到的极帽饱和电位的能力。本研究中最具挑战性的方面是跨尺度耦合的处理，以及将无碰撞微物理效应以异常输运的形式纳入流体和电动力学模型。这项研究将使学生接触到跨学科的研究，因为它涉及到计算机模拟和建模，应用于核聚变和等离子体物理、气象学，以及复杂物理和生物系统的总体研究。

The objective of this research is to develop a physics-based module of the ionospheric conductivity that incorporates anomalous heating due to the electrojet instability driven by strong convection electric fields in the ionosphere. Reliable dynamic ionospheric conductance and energy dissipation modules covering the entire range of the solar wind input are critical elements in the construction of global electrodynamic ionosphere-magnetosphere models, such as the Geospace General Circulation Model (GGCM), the Global Ionospheric Model (GIM) and the TIME-GCM Model. Furthermore, they are critical in the representation of the ionospheric boundary in global magneto-hydrodynamic codes. A semi-empirical model based on a simple prescription is used in the LFM model, while an assimilation model, the Assimilating Mapping of Ionospheric Electrodynamics (AMIE) is the frontrunner for incorporation to the GGCM. The modeling and comparison with data shows that the above models perform well under conditions of moderate ( 20 mV/m) local ionospheric electric fields. Under strong ( 20 mV/m) local ionospheric electric fields, an important energy dissipation mechanism due to the electron Hall current becomes important. This process is not included in the traditional ionospheric electrodynamic energy budget, since the current and the electric field are orthogonal to each other. The dissipation is thus anomalous and is attributed to well known and experimentally documented Farley-Buneman two-stream electrojet instability. Electron temperatures in excess of 2000 K have been observed by the EISCAT radar and earlier by the Chatanika radar at E-region altitudes. The process, in addition to acting as a non-Ohmic dissipation, results in changes in the Pederson and Hall conductances by modifying the electron recombination coefficient and thus increasing the resultant plasma density. In this study, appropriate algorithms will be developed for incorporation in the AMIE, GIM, TIME-GCM and to global MHD codes. The new conduction module will be disseminated to the broader space science community to assess its ability to represent the observed saturation of the polar cap potential. The most challenging aspects of this research are the treatment of cross scale coupling and the incorporation of collisionless microphysics effects into fluid and electrodynamic models in the form of anomalous transport. The study will expose students to interdisciplinary research because it involves computer simulations and modeling with applications to fusion and plasma physics, meteorology, and overall to studies of complex physical and biological systems.