Extreme Events in Geospace

Origins, Predictability, and Consequences

Natalia Buzulukova

• Publisher: Elsevier
• Year: 2017
• Print ISBN: 9780128127001
• eBook ISBN: 9780128127018
• Topic: Physical Sciences
• Subtopic: Astronomy & Astrophysics

Extreme Events in Geospace: Origins, Predictability, and Consequences helps deepen the understanding, description, and forecasting of the complex and inter-related phenomena of extreme space weather events. Composed of chapters written by representatives from many different institutions and fields of space research, the book offers discussions ranging from definitions and historical knowledge to operational issues and methods of analysis.Given that extremes in ionizing radiation, ionospheric irregularities, and geomagnetically induced currents may have the potential to disrupt our technologies or pose danger to human health, it is increasingly important to synthesize the information available on not only those consequences but also the origins and predictability of such events. Extreme Events in Geospace: Origins, Predictability, and Consequences is a valuable source for providing the latest research for geophysicists and space weather scientists, as well as industries impacted by space weather events, including GNSS satellites and radio communication, power grids, aviation, and human spaceflight.The list of first/second authors includes M. Hapgood, N. Gopalswamy, K.D. Leka, G. Barnes, Yu. Yermolaev, P. Riley, S. Sharma, G. Lakhina, B. Tsurutani, C. Ngwira, A. Pulkkinen, J. Love, P. Bedrosian, N. Buzulukova, M. Sitnov, W. Denig, M. Panasyuk, R. Hajra, D. Ferguson, S. Lai, L. Narici, K. Tobiska, G. Gapirov, A. Mannucci, T. Fuller-Rowell, X. Yue, G. Crowley, R. Redmon, V. Airapetian, D. Boteler, M. MacAlester, S. Worman, D. Neudegg, and M. Ishii.- Helps to define extremes in space weather and describes existing methods of analysis- Discusses current scientific understanding of these events and outlines future challenges- Considers the ways in which space weather may affect daily life- Demonstrates deep connections between astrophysics, heliophysics, and space weather applications, including a discussion of extreme space weather events from the past- Examines national and space policy issues concerning space weather in Australia, Canada, Japan, the United Kingdom, and the United States

Part 1

Overview of Impacts and Effects

Chapter 1

Linking Space Weather Science to Impacts—The View From the Earth

Mike Hapgood RAL Space, STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
Space and Planetary Physics Group, Lancaster University, Lancaster, United Kingdom

Abstract

This chapter explores how we can link space weather science to impacts. It stresses the value of tracing space weather from its societal impacts on human activities on Earth back to its origin on the Sun, thus enabling us to more clearly identify the solar, heliospheric, and terrestrial phenomena that are crucial to assessing and forecasting the societal impacts of space weather. The chapter also presents a structure that consolidates most space weather impacts into four major topics: (1) the geoelectric fields that drive geomagnetically induced currents; (2) the complex behavior of the upper atmosphere and its seemingly diverse impacts on radio systems and satellite orbits; (3) the atmospheric radiation that increasingly disrupts digital devices, both on aircraft and on the ground; and (4) the interaction of satellites with the rich plasma environments that fill many operational orbits, not least the vital geosynchronous ring. This focus on major topics provides a way of simplifying the links between science and impacts, which can otherwise appear as a long and complex list of impact areas that risk being boring and confusing because of the diversity of space weather effects. It facilitates an understanding of how the science links to impacts—especially in extreme space weather conditions. In a final section we look to the future and consider how space weather risks may evolve. We review a number of technological developments that may change our perception of space weather risks in the next few decades. This includes areas in which new technologies may open up new space weather risks as well as areas in which new technologies may retire current space weather risks.

Keywords

Space weather; Societal impact; Geomagnetically induced currents; Single-event effects; Scintillation; Satellite drag; Ionospheric group delay; Satellite charging

Chapter Outline

1 Introduction

2 Space Weather Environments at Earth

3 Geomagnetically Induced Currents—The Impacts of Natural Geoelectric Fields

4 Space Weather Impacts on the Upper Atmosphere

4.1 Overview of the Upper Atmosphere

4.2 Trans-Ionospheric Radio Propagation

4.3 Atmospheric Drag

4.4 Atmospheric Radiation Environment

4.5 Satellite Plasma Environments

4.6 Looking to the Future: How May Space Weather Risks Evolve?

References

1 Introduction

Scientific discussions of space weather and impacts traditionally start with a discussion of the solar sources of space weather. They then trace along the flow of energy and momentum through the solar wind to the Earth, then to terrestrial environments where space weather interacts with technology. This is a very natural approach for anyone with a physics background—follow the energy flow. In this chapter we will take the opposite approach by tracing space weather from its societal impacts on human activities on Earth back to its origin on the Sun. This reverse approach has an important advantage in that it enables us to more clearly identify the solar, heliospheric, and terrestrial phenomena that are crucial to assessing and forecasting the societal impacts of space weather, since it ensures we follow the chains of physical processes that produce significant impacts.

It is also worth noting that some space weather phenomena have sources other than the Sun. Galactic cosmic rays are a population of protons and ions that are accelerated to GeV and above energies by shocks produced by supernovae elsewhere in our galaxy. They pervade the galaxy, including our solar system, but turbulence in the heliospheric magnetic field scatters many of these particles so that they do not reach the inner solar system. Nonetheless, a substantial fraction of cosmic rays do reach Earth, a fraction that varies with solar activity (Chapter 13 of this volume). These cosmic rays produce significant radiation effects on satellites and the Earth, and must be considered in any discussion of space weather impacts. Phenomena in the troposphere also contribute to space weather. The strong electric fields in large thunderclouds can generate a variety of energetic phenomena—not just lightning, but also very bright (equaling the brightest aurora) and very short-lived (milliseconds) luminous phenomena in the stratosphere and mesosphere above the clouds (Chapter 19 of this volume). We need to understand extreme instances of transient luminous events so as to assess whether they pose a risk to suborbital space flights and hypersonic aircraft now being developed. Large thunderclouds and other strong convective activity in the troposphere can also generate atmospheric gravity waves that can transport energy and momentum to the upper atmosphere, where they are thought to drive up to 50% of day-to-day space weather variations in the ionosphere and thermosphere (Liu et al., 2013). However, it is not clear if they play any role in extreme space weather events.

The adverse impacts of space weather at Earth encompass a wide and growing range of technological systems, a range that can seem bewildering at times (see Fig. 1). However, these impacts arise from a limited number of terrestrial environments—more precisely from how space weather modifies those environments in ways that disrupt various technologies.

Fig. 1 An overview of space weather processes and impacts, highlighting some of the interrelationships between different effects. Many space weather effects will occur close together in time as they have a common origin in solar phenomena such as coronal mass ejections. This figure outlines the most important associations between space weather effects. The vertical transport of energy and momentum from the troposphere is omitted because of its complexity but may play a role in several system impacts.

The next section summarizes those environments and outlines how space weather leads to disruptive conditions. Later sections will explore in detail some of the major technological impacts arising from those environments, and a final section will outline likely changes in those impacts given current trends in technology development. These later sections seek to give the reader insights into many key space weather impacts, but do not aim to be comprehensive of every impact. The latter is almost impossible due to the diversity of space weather phenomena and their impacts.

2 Space Weather Environments at Earth

1. The natural geoelectric fields that exist on the surface of the Earth. These are driven by time-varying magnetic fields, in particular those that arise from electric currents flowing in Earth's ionosphere and magnetosphere and that are strongly modulated by a range of space weather effects from the Sun. These geoelectric fields drive unexpected electric currents into any metallic infrastructures that are electrically connected to the surface of the Earth (Chapter 8 of this volume). That electrical “grounding” is an essential design feature of most infrastructures, ensuring electrical safety and sometimes also electromagnetic compatibility with devices near the infrastructure. Power grids are the key infrastructure in this class, which also includes power and control systems on railways; pipelines such as those used for transmission of oil and gas; and power systems on the fiberoptic cables that run under the oceans (a mainstay of modern Internet and voice communications).

2. The upper atmosphere above about 90 km, both its neutral and ionized components (thermosphere and ionosphere), up to at least 1000 km. The dynamics of this region are dominated by space weather. For example, variations in solar EUV emissions control the heat inputs that drive thermospheric winds and the consequent plasma flows in the ionosphere (King and Kohl, 1965). These emissions also control the ionization rates that create the ionosphere. Variations in the solar wind electric field can sometimes penetrate the magnetosphere and drive unusual plasma flows in the ionosphere, such as the uplift and associated density increases seen early in geomagnetic storms. Energy inputs from solar wind can create intense heating in the polar thermosphere, leading to profound changes in the global circulation of the thermosphere. That heating can also inject molecular species such as nitric oxide (NO) into the thermosphere leading to more rapid loss of ionization via dissociative recombination, and hence the night-time disappearance of the ionosphere that is a distinctive feature of the later phases of geomagnetic storms. In summary, the upper atmosphere is a complex dynamic system comprising neutral and ionized components that are weakly coupled and that both respond strongly to space weather. The neutral component is important technologically because it provides the atmospheric drag that modifies the orbits of satellites passing through this region. Space-weather-induced changes in this drag present a challenge to satellite operators who need accurate orbit predictions to plan satellite operations as well as assess collision risks and re-entry times. In extreme space weather conditions, such as the March 1989 storm, it can lead to loss of knowledge of the positions of thousands of objects in low Earth orbit (LEO) (Air University, 2003). The ionized component is important technologically because of the huge number of systems that use radio signals that are affected by their passage through the ionosphere. These cover frequencies ranging from 50 kHz up to 4 GHz, with lower frequencies (up to 10 or 20 MHz) being reflected and higher frequencies subject to group delay (as the group refractive index of the ionospheric plasma is slightly greater than one) and scintillation (due to plasma instabilities that create fine structures and turbulence in the ionosphere). Frequencies from 1 to 100 MHz can also be subject to absorption. These space weather impacts from the upper atmosphere mostly arise at altitudes below 1000 km. For example, the neutral densities above this altitude are too low to produce significant drag on satellites. But the long path lengths through the tenuous plasma that extends out to 20,000-km altitude (the plasmasphere) can contribute significantly to group delay of GNSS signals (Lunt et al., 1999).

3. Atmospheric radiation environment (up to 100 km). Natural radiation includes a contribution from sources in space. There is a slowly changing background of galactic cosmic rays that produces about 8% of the natural radiation background at sea level, but that dominates above 3-km altitude. The atmospheric radiation produced by galactic cosmic rays includes neutrons that can penetrate electronic devices, both on aircraft and on the ground, leading to single-event effects that cause those devices to malfunction or suffer damage. Electronic devices involved in safety-critical applications such as aircraft control are usually designed to mitigate these effects. During major space weather events, solar energetic particles (MeV to GeV protons and ions, energized at shocks ahead of fast coronal mass ejections (CMEs) and at solar flare reconnection sites) can deliver a huge increase in the natural radiation levels for a few hours. The worst observed case was an event in February 1956 that produced a 50-fold increase at the ground (Gold and Pa...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Author Biography’s
• Foreword
• Acronyms
• Introduction
• Part 1: Overview of Impacts and Effects
• Part 2: Solar Origins and Statistics of Extremes
• Part 3: Geomagnetic Storms and Geomagnetically Induced Currents
• Part 4: Plasma and Radiation Environment
• Part 5: Ionospheric/Thermospheric Effects and Impacts
• Part 6: Dealing with the Space Weather
• Index