Key concepts

• electromagnetic radiation

• heat transfer

• Standard Solar Model

• solar atmosphere

• solar cycle

Introduction

Since the dawn of man, the Sun has elicited worship, inspiration, and study, and tremendous mysteries about its dynamics still occupy the attention of solar astronomers and space physicists. This ignorance has profound implications. We now rely on space for global communication, navigation, and Earth observing, and solar dynamics cause degradation and failure of satellites and space instruments. Understanding solar dynamics is a key part of understanding space weather. This chapter describes what we know about the Sun and how we know it. Much of our knowledge comes from observations of the Sun, and much of it comes from applying the laws of physics (such as thermodynamics and nuclear and atomic physics) within quantitative models to make predictions of observable quantities. This is how we know what goes on inside the core of the Sun without going there or observing it directly. This combination of observation and physics as all owed us to know more about our natural surroundings than at any other time in human history.