Parallel sessions

Solar activity Cycle 24 has been significantly weaker than the previous few cycles. These changes were signposted by the unusually extended and deep solar minimum at the boundary of Cycles 23 and 24. Some activity indicators dropped to remarkably low values during the Cycle 23/24 minimum, e.g. the geomagnetic aa-index and the sunspot number. Helioseismology has also revealed unusual signatures related to near-surface flow patterns and subtle changes in structure. Very few of the predictions collated by the Solar Cycle 24 Prediction Panel forecast the extent of the minimum or the low levels of activity that followed. One must go back around one-hundred years to find cycles that show levels of activity as low as those observed in Cycle 24, an epoch predates both the modern Grand Maximum period and the satellite era. Ongoing studies of the unusual behaviour of the Sun have been accompanied by recent intriguing developments in studies of other Sun-like stars, ushered in by Kepler and the advent of “micro-magnitude” precision photometric studies of stars. Results combining data on surface rotation with new high-precision constraints on stellar ages suggest that stars at about the age of the Sun may undergo radical changes in the operation of their dynamos (as signaled by a decline in the efficiency of magnetic braking of rotation).

In this session we aim to bring together scientists from the solar and heliospheric communities to explore results from a wide variety of data -- solar atmosphere, interior and heliospheric -- that bear on the unusual Cycle 24, its causes, and what the results might signal for the next cycle. We also wish to attract scientists from the stellar community to bring to bear observational results on Sun-like stars that may help to inform our understanding of the Sun's behaviour.

We note that there will be an opportunity to explore stellar dynamos over a wider range of stars in the parallel session "Generation and Evolution of Solar and Stellar Magnetic Fields, and Implications for the Solar-Stellar Connection".