Over the past few centuries, our awareness of the couplings between the Sun's variability and the Earth's environment, and perhaps even its climate, has been advancing at an ever increasing rate. The Sun is a magnetically variable star and, for planets with intrinsic magnetic fields, planets with atmospheres, or planets like Earth with both, there are profound consequences and impacts. Today, the successful increase in knowledge of the workings of the Sun's magnetic activity, the recognition of the many physical processes that couple the realm of the Sun to our galaxy, and the insights into the interaction of the solar wind and radiation with the Earth's magnetic field, atmosphere, and climate system have tended to differentiate and insularize the solar, heliospheric, and geospace sub-disciplines of the physics of the local cosmos. In 2001, the NASA Living With a Star (LWS) program was initiated to reverse that trend.

The recognition that there are many connections within the Sun–Earth systems approach has led to the development of an integrated strategic mission plan and a comprehensive research program encompassing all branches of solar, heliospheric, and space physics, and aeronomy. In doing so, we have developed an interdisciplinary community to address this program. This has raised awareness and appreciation of the research priorities and challenges among the LWS scientists and has led to observational and modeling capabilities that span traditional discipline boundaries.

Introduction

The volumes on heliophysics, of which this is the third, emphasize universal processes for which some basic physical phenomenon manifests itself in a variety of circumstances throughout the local cosmos and beyond. The topics range from the variability of the star next to which we live to the distant interstellar medium, via planetary environments including, in particular, geospace in which a magnetic field and atmosphere shield us from most of the dangerous consequences of solar variability – taking us from solar flares, coronal mass ejections, and their associated energetic particles, via the dynamic interplanetary medium, to magnetospheric, ionospheric, and tropospheric consequences. This volume in particular emphasizes interconnectedness, which manifests itself in three different guises that appear, often implicitly, throughout the text.

First, there is the interconnectedness by the universal processes themselves: magnetohydrodynamics, radiative transfer, networks of chemical reactions, magnetic-field dynamics and topology, particle acceleration, shocks, turbulence, etc., pervade all three volumes. Second, we see the interconnectedness in the very evolution of the solar system, from the formation of the central star and its orbiting planets, to the impact of the star on planetary habitability, and the eventual demise of the solar system as we know it (Fig. 1.1). Third, there are many connections between a variety of research disciplines, each of which is advanced by what is learned from other disciplines, thus providing mutual support in their quest for deeper understanding.

Over the past few centuries, our awareness of the couplings between the Sun's variability and the Earth's environment, and perhaps even its climate, has been advancing at an ever increasing rate. The Sun is a magnetically variable star and for planets with intrinsic magnetic fields, planets with atmospheres, or planets like Earth with both, there are profound consequences and impacts. Today, the successful increase in knowledge of the workings of the Sun's magnetic activity, the recognition of the many physical processes that couple the realm of the Sun to our galaxy, and the insights into the interaction of the solar wind and radiation with the Earth's magnetic field, atmosphere and climate system have tended to differentiate and isolate the solar heliospheric and geo-space sub-disciplines of the physics of the local cosmos. In 2001, the NASA Living With a Star (LWS) program was initiated to reverse that trend.

The recognition that there are many connections within the Sun–Earth systems approach has led to the development of an integrated strategic mission plan and a comprehensive research program encompassing all branches of solar, heliospheric, and space physics and aeronomy. In doing so, we have developed an interdisciplinary community to address this systems-science. This has raised awareness and appreciation of the research priorities and challenges among the LWS scientists and has led to observational and modeling capabilities that span traditional discipline boundaries. The successful initial integration of the LWS sub-disciplines, under the newly coined term “heliophysics”, needed to be expanded into the early education of scientists.