Published online by Cambridge University Press: 08 February 2017
Although the rate of production of nuclear energy in the sun's core almost certainly increases smoothly on time scales shorter than and comparable to the solar age, the mechanisms transporting this energy to the photosphere may be subject to more erratic fluctuations. Indeed space observations establish that the total solar irradiance in the direction of the earth is variable on time scales of days to years. I discuss energy transport by convection and magnetic fields with consideration of the possibility of energy storage through changes in the solar radius. Convection is the primary means of energy transport below the solar surface and must be involved in any modulation of energy flow. The large scale and long duration properties of solar convection arising from zones below the solar surface can be well studied using the Michelson-Doppler Imager instrument on SOHO. New evidence of long duration convective structures based on the MDI data is presented. These patterns appear to be related to the torsional oscillations observed at the Mt. Wilson Observatory.