The Dynamical Ionosphere

A Systems Approach to Ionospheric Irregularity

Massimo Materassi, Biagio Forte, Anthea J. Coster, Susan Skone

• Publisher: Elsevier
• Year: 2019
• Print ISBN: 9780128147825
• eBook ISBN: 9780128147832
• Topic: Physical Sciences
• Subtopic: Geophysics

The Dynamical Ionosphere: A Systems Approach to Ionospheric Irregularity examines the Earth's ionosphere as a dynamical system with signatures of complexity. The system is robust in its overall configuration, with smooth space-time patterns of daily, seasonal and Solar Cycle variability, but shows a hierarchy of interactions among its sub-systems, yielding apparent unpredictability, space-time irregularity, and turbulence. This interplay leads to the need for constructing realistic models of the average ionosphere, incorporating the increasing knowledge and predictability of high variability components, and for addressing the difficulty of dealing with the worst cases of ionospheric disturbances, all of which are addressed in this interdisciplinary book.Borrowing tools and techniques from classical and stochastic dynamics, information theory, signal processing, fluid dynamics and turbulence science, The Dynamical Ionosphere presents the state-of-the-art in dealing with irregularity, forecasting ionospheric threats, and theoretical interpretation of various ionospheric configurations.- Presents studies addressing Earth's ionosphere as a complex dynamical system, including irregularities and radio scintillation, ionospheric turbulence, nonlinear time series analysis, space-ionosphere connection, and space-time structures- Utilizes interdisciplinary tools and techniques, such as those associated with stochastic dynamics, information theory, signal processing, fluid dynamics and turbulence science- Offers new data-driven models for different ionospheric variability phenomena- Provides a synoptic view of the state-of-the-art and most updated theoretical interpretation, results and data analysis tools of the "worst case" behavior in ionospheric configurations

Part I

The earth’s ionosphere, an overview

Chapter 1

Introduction

Michael Mendillo Department of Astronomy, Boston University, Boston, MA, United States

Abstract

The terrestrial ionosphere has many components with interdependencies and feedback loops. It displays multiple networks of connectivity, with different spatial and temporal modes of adaptations to stress. Collectively, the result is a high level of diversity in structures and temporal patterns—making the ionosphere a complex natural system.

Keywords

Formation of the ionosphere; Ionospheric layers; Latitude domains

An ionosphere is that portion of a planet’s upper atmosphere where solar photons impact neutral gases to yield a plasma of electrically charged ions and electrons. The basic physics and chemistry that govern terrestrial ionospheric structure and dynamics have been treated in a robust series of fundamental reference books (Ratcliffe, 1960; Rishbeth and Garriott, 1969; Banks and Kockarts, 1973; Rees, 1989; Hargreaves, 1995; Prölss, 2004; Kelley, 2009; Knipp, 2011). Extensions of ionospheric theory to other planets in our solar system are given in the monographs by Bauer (1973), Mendillo et al. (2002), Bauer and Lammer (2004), and Nagy et al. (2008). The most unified treatment of terrestrial and planetary ionospheric science is given in the comprehensive textbook by Schunk and Nagy (2009). Given these excellent sources of educational material, and a readership with experience in ionospheric research, this introductory chapter will not present a detailed repetition of theory. Rather, the goal is to set the stage for the innovative treatment of the Earth’s ionosphere as a complex system, as presented in the chapters that follow.

Historically, ionospheric theory was approached as a unique solar-terrestrial phenomenon linking solar photons with the Earth’s neutral gases to yield a plasma population capable of being studied using ground-based instrumentation. Within this framework, the ionosphere is produced by a flux of solar photons versus wavelength (called “irradiance”)—ranging from X-rays (<~10 nm) to extreme ultraviolet (<~120 nm). Collectively called XUV radiation, these photons penetrate to different heights in the upper atmosphere to ionize the primary gases N₂, O₂, and O. The strength of the XUV radiation varies over time scales ranging from minutes (solar flares) to decades (solar cycle). For a fixed daily value at the subsolar point, the ionizing radiation varies with latitude and local time (collectively described by solar zenith angle).

The fact that the solar irradiance components reach different altitudes resulted in each of the textbooks mentioned earlier describing the vertical structure of the ionosphere as a series of “layers” produced at different photon penetration heights. Similarly, the latitude structure was described as a series of zones ordered by solar zenith angles and magnetic field characteristics along north-south meridians. Thus, as shown in Fig. 1, the ionosphere was presented as having D, E, F1, and F2 layers in altitude, with each of these layers varying in latitude from the polar cap to the equator—subdividing the near-space environment into auroral, subauroral, middle, low and equatorial ionospheric regimes. This view produced a high level of understanding of individual processes acting within the global ionosphere. Yet, such a compartmentalization of the ionosphere is purely historical and today seems as a somewhat limiting framework for progress. This ensemble-of-layers approach arose simply from sequential applications of the initial formulation of ionospheric theory within the context of photo-chemical-equilibrium conditions (Chapman, 1931). So powerful was the respect for Sydney Chapman’s pioneering portrayal of the ionosphere that any observational departure from Chapman Theory was called an anomaly (e.g., seasonal anomaly, diurnal anomaly, equatorial anomaly). In reality, the shortfalls were in the physics used, and not with questionable diagnostic findings.

Fig. 1 Layers of the Earth’s ionosphere. From Bauer, S.J., Lammer, H., 2004. Planetary Aeronomy. Springer, New York.

With the coming of the Space Age, new satellite instruments, much-improved radio and optical observing methods from the ground, and advanced computer modeling capabilities ushered in the modern era of ionospheric research. The quaint notion of individual electrified layers stacked on top of each other, with latitude zones isolated from each other, has been replaced by the new paradigm of coupling.

The historical foundation for coupling within the geospace domain had been set decades earlier via explanations of the causes of aurora. Thus, magnetosphere-ionosphere (M-I) coupling at high latitudes set the precedent for additional understanding of space physics system-science. Today, solar-terrestrial relationships involve far more than the photon source of the ionosphere. The chain of events leading to complexity starts with a coronal mass ejection producing modified solar wind plasma density, velocity, and magnetic field characteristics. These, in turn, cause solar wind-magnetosphere coupling—followed by M-I coupling. This classic scenario of Sun-Earth space physics is summarized schematically in Fig. 2. Yet, there is an additional component of coupling also shown in Fig. 2 that emerged from more recent research. When ionospheric variability was found to be substantial during periods of very quiescent solar and magnetospheric conditions, a source of nondownward coupling was needed. This led to the concept of coupling from below—completing the paradigm of the ionosphere being a fully linked surface-to-Sun atmospheric-plasma system.

Fig. 2 Coupling components of upper atmosphere regions (NASA image).

Altitude and latitude coupling on a global scale have introduced levels of complexity that are now the major foci of ionospheric research. This chapter is a prelude to the issues treated in subsequent chapters—where various types of complexity—a term still difficult to define (Charbonneau, 2017)—are introduced and described. Here, the agenda is set by describing a few processes that are not simply latitude or altitude dependent. Such topics illuminate core concepts of altitude and latitude coupling, but treat them as universal processes. The focus is on a difference in approach to problems formerly treated as issues confined by spatial and temporal boundaries. The goal is to continue fostering a transition of thinking about the ionosphere as depicted in Fig. 1 to the system depicted in Fig. 2.

References

Banks P.M., Kockarts G. Aeronomy (Parts A and B). New York: Academic Press; 1973.

Bauer S. Physics of Planetary Ionospheres. Berlin: Springer-Verlag; 1973.

Bauer S.J., Lammer H. Planetary Aeronomy. New York: Springer; 2004.

Chapman S. The absorption and dissociation or ionizing effect of monochromatic radiation in an atmosphere on a rotating earth. Proc. Phys. Soc. Lond. 1931;43:26–45.

Charbonneau P. Natural Complexity: A Modeling Handbook. Princeton, NJ: Princeton University Press; 2017.

Hargreaves J.K. The Solar-Terrestrial Environment. Cambridge: Cambridge University Press; 1995.

Kelley M. The Earth’s Ionosphere: Plasma Physics and Electrodynamics. second ed. New York: Elsevier Academic Press; 2009.

Knipp D.J. Understanding Space Weather and the Physics Behind It. Boston, MA: McGraw Hill; 2011.

Mendillo M., Nagy A., Waite J.H., eds. Atmospheres in the Solar System: Comparative Aeronomy. Washington, DC: American Geophysical Union; 2002. Geophysical Monograph 130..

Nagy A.F., Galogh A., Cravens T.E., Mendillo M., Muller-Wodarg I., eds. Comparative Aeronomy. Berlin: Springer; 2008 (also in Space Science Reviews, vol. 139, no. 1-4.).

Prölss G.W. Physics of the Earth’s Space Environment: An Introduction. Berlin: Springer-Verlag; 2004.

Ratcliffe J.A., ed. Physics of the Upper Atmosphere. New York: Academic Press; 1960.

Rees M.H. Physics and Chemistry of the Upper Atmosphere. Cambridge: Cambridge University Press; 1989....

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Preface
• Part I: The earth’s ionosphere, an overview
• Part II: Global complexity
• Part III: Local irregularities
• Part IV: The future era of ionospheric science
• Index