Sarris Theodore E
Department of Electrical and Computer Engineering, Democritus University of Thrace , University campus of Xanthi-Kimmeria, Building B, Xanthi 67132 , Greece.
Philos Trans A Math Phys Eng Sci. 2019 Jul 1;377(2148):20180101. doi: 10.1098/rsta.2018.0101.
The ionosphere and thermosphere (IT) constitutes a coupled, complex and dynamical electromagnetic and photochemical system, which is sensitive to a combination of external factors: particle precipitation and electrical currents from the Earth's magnetosphere and incoming solar radiation produce dramatic effects in the IT and significantly alter its energetics, dynamics and chemistry in a way that is not well understood. This sensitivity of the IT to external factors results in large, yet often unpredictable changes in many of the variables in the IT, such as in its density, temperature, neutral and ion winds, total electron content, neutral and ion composition, electric fields, currents and conductivities. External forcing of the IT system varies over different time-scales, such as solar cycle (11-year), inter-annual (e.g. quasi-biennial), seasonal and diurnal; on top of these, geomagnetic disturbances caused by solar storms and substorms can lead to abrupt reconfigurations of the magnetospheric field-aligned and horizontal currents, setting a number of electrodynamics processes in motion. The overlapping physical and chemical phenomena occur at a range of temporal and spatial scales that are highly difficult to understand as a whole. The importance of the behaviour of this region to multiple issues related to aerospace technology, such as orbital calculations, vehicle re-entry, space debris lifetime, etc., and its potential threats to modern, technology-dependent society via geomagnetically induced currents and ionospheric scintillation of Global Navigation Satellite System signals, dictate that a more detailed understanding and accurate modelling are urgently needed. In this paper, we review the status of characterization and some of the key open issues and challenges of the IT, focusing on measurement gaps in this region as well as areas of largest discrepancies between models and data. This article is part of the theme issue 'Solar eruptions and their space weather impact'.
电离层和热层（IT）构成了一个耦合的、复杂的动态电磁和光化学系统，该系统对多种外部因素的组合敏感：来自地球磁层的粒子沉降和电流以及入射太阳辐射在IT中产生显著影响，并以一种尚不清楚的方式显著改变其能量学、动力学和化学性质。IT对外部因素的这种敏感性导致IT中的许多变量发生巨大但往往不可预测的变化，例如其密度、温度、中性和离子风、总电子含量、中性和离子组成、电场、电流和电导率。IT系统的外部强迫在不同的时间尺度上变化，如太阳周期（11年）、年际（如准两年）、季节和昼夜尺度；除此之外，由太阳风暴和亚暴引起的地磁扰动可导致磁层场向电流和水平电流的突然重新配置，引发一系列电动力学过程。重叠的物理和化学现象发生在一系列时间和空间尺度上，整体上极难理解。该区域的行为对与航空航天技术相关的多个问题（如轨道计算、飞行器重返大气层、空间碎片寿命等）的重要性，以及它通过地磁感应电流和全球导航卫星系统信号的电离层闪烁对依赖技术的现代社会构成的潜在威胁，都表明迫切需要更详细的理解和精确的建模。在本文中，我们回顾了IT的特征描述现状以及一些关键的未解决问题和挑战，重点关注该区域的测量空白以及模型与数据之间差异最大的领域。本文是主题为“太阳爆发及其空间天气影响”的一部分。
