  A striking feature of the solar cycle is that at the beginning, sunspots
appear around mid-latitudes, and over time the latitudes of emergences migrate
towards the equator. The maximum level of activity varies from cycle to cycle.
For strong cycles, the activity begins early and at higher latitudes with wider
sunspot distributions than for weak cycles. The activity and the width of
sunspot belts increase rapidly and begin to decline when the belts are still at
high latitudes. However, in the late stages of the cycles, the level of
activity, and properties of the butterfly wings all have the same statistical
properties independent of the peak strength of the cycles. We have modelled
these features using Babcock-Leighton type dynamo model and shown that the
toroidal flux loss from the solar interior due to magnetic buoyancy is an
essential nonlinearity that leads to all the cycles decline in the same way.
