Reconstruction Of Solar Irradiance Variations In Cycles 21 23 Based On Surface Magnetic Fields

Reconstruction of Solar Irradiance Variations in Cycles 21-23 Based on Surface Magnetic Fields

The Solar Activity Cycle

A collection of papers edited by four experts in the field, this book sets out to describe the way solar activity is manifested in observations of the solar interior, the photosphere, the chromosphere, the corona and the heliosphere. The 11-year solar activity cycle, more generally known as the sunspot cycle, is a fundamental property of the Sun. This phenomenon is the generation and evolution of magnetic fields in the Sun’s convection zone, the photosphere. It is only by the careful enumeration and description of the phenomena and their variations that one can clarify their interdependences. The sunspot cycle has been tracked back about four centuries, and it has been recognized that to make this data set a really useful tool in understanding how the activity cycle works and how it can be predicted, a very careful and detailed effort is needed to generate sunspot numbers. This book deals with this topic, together with several others that present related phenomena that all indicate the physical processes that take place in the Sun and its exterior environment. The reviews in the book also present the latest theoretical and modelling studies that attempt to explain the activity cycle. It remains true, as has been shown in the unexpected characteristics of the first two solar cycles in the 21st century, that predictability remains a serious challenge. Nevertheless, the highly expert and detailed reviews in this book, using the very best solar observations from both ground- and space based telescopes, provide the best possible report on what is known and what is yet to be discovered. Originally published in Space Science Reviews, Vol 186, Issues 1-4, 2014.

Solar Variability and Planetary Climates

2 With a global average irradiance of 342 W/m , the Sun is by far the largest source of energy for planet Earth. In comparison, the internal energy produced by Earth 2 itself is only about 0. 087 W/m (Pollack et al. , 1993), which in turn is 3. 5 times 2 larger than the 0. 025 W/m of heat produced by the burning of fossil fuels. About 31% (31 units) of the solar energy which arrives at the top of the - mosphere is re?ected back to space by scattering from clouds, aerosols, and the Earth’s surface. Almost 20 units of solar radiation are absorbed in the atmosphere. The remaining 49 units are absorbed at the surface. Evaporation of water at the Earth’s surface consumes 23 units, and 7 units are transferred to the atmosphere by heat conduction. On balance 19 units are lost from the Earth’s surface as infrared radiation, however consisting of 114 going upward and 95 returning from the - mosphere to the Earth’s surface (see also Rosenfeld, 2006). There is thus a sixfold recycling of energy. This is the greenhouse effect, established by the presence of watervaporandofothergreenhousegases,CO ,CH ,N O,andCFCs,intheatmo- 2 4 2 sphere. Due to human activities the latter have been increasing in the atmosphere, 2 causing climate warming through an energy imbalance of 2. 5–3 W/m , more than 100 times larger than the heat released into the atmosphere by the burning of fossil fuels.