Probing the Solar Interior: Solar Activity Cycle Inferences from Helioseismology
The Variable Sun: Cycles, Waves, Oscillations, and Instabilities
Anne-Marie Broomhall
University of Warwick
Helioseismology uses the Sun’s natural oscillations to probe beneath the solar surface. At any one time, thousands of oscillations are trapped in different but overlapping regions of the solar interior. By studying the properties of these oscillations, such as their frequencies, we can probe inside the Sun. It has been known for some time that the frequencies of solar oscillations very systematically throughout the Sun’s 11yr magnetic activity cycle, with the frequencies being highest at solar activity maximum. Helioseismology thus allows us to study the relationship between the internal structure of the Sun and its magnetic field. Helioseismology can also be used to infer the structure of flows in the solar interior, such as the torsional oscillation, which also vary on timescales that can be associated with the solar cycle. We are now in an epoch where there is sufficiently long helioseismic data available to compare different activity cycles. Helioseismology has revealed that it is not just the solar surface and overlying atmosphere where differences between the current solar cycle and previous, recent cycles have been observed. In fact the helioseismic data indicate that the solar interior displayed a change in behaviour well before the recent minimum. I will review the recent advances in helioseismology in relation to the solar cycle, discussing inferences that can be made about the solar interior as the current weak activity cycle evolves.
09:00 - 10:30