Solar Cycle 24 activity has peaked and it is trending down to minimal Sunspot numbers. As most Solar Cycles are nominally 11 years in length, one might guess that December 2019 would be the end of Cycle 24 and the start of Solar Cycle 25. But don’t bet too much money on that date. Eleven years is 132 months. But Cycle 23 was not completed until 149 months after it began. The chart (courtesy of Solen.info) below shows the current state of Cycle 24:
Looking at the Solar Cycle 24 progress chart (courtesy of Solen.info) below one can see that the South Polar Field (green line) has been the source of most of the Sunspot activity the past year or so. And it has really taken a tumble since midyear.
Adding the South and the North polar fields Sunspot production gives us the average Sunspot number (black line.) The November number was 63.2. The projected smoothed number for November is 64.5.
Maybe examining the polar fields will gives us some idea where Cycle 24 is headed and maybe even some ideas about Cycle 25. The Solar Polar Field Strengths for Cycles 21, 22, 23 and 24 are shown on the following chart (courtesy of Solen.info):
On the chart above, one can see the path of the South and the North polar fields as they move from the poles to equator. When they cross, they reverse their polarity (but not their designation). The maximum solar activity, as defined by numbers of Sunspots, happens when the fields cross the Sun’s equator. The beginning and ending of each Cycle are defined by when the Sunspot production is the minimum. The maximum and the minimum calls always seem to be a bit of arbitrary to me, but it has no real consequences. The maximum and the minimum are pinpointed by the pink and the green lines on the chart.
The next chart (courtesy of solen.info) illustrates more clearly the differences between the Cycles:
The black line is the smoothed average of the two polar strengths. For orientation, this chart holds Cycles 21,22,23 and 24.
|Cycle No.||Start of Cycle|
Beginning at the right hand side of the chart, go back to approximately December 2008. That is the start of Cycle 24. So you can see that each of the Cycles portrayed on this chart are half of a sine wave. Cycle 24 is clearly different from the preceding three Cycles. The half sine waves for 21, 22 and 23 are much deeper and much steeper than 24. Based upon the Sunspots at maximum for these 4 Cycles, solar activity is nominally indicative of the depth and the steepness of the polar field strength. The question is, what will the Solar Cycle 24 plot look like say 3 years from now. If we knew, a reasonably accurate prediction of Solar Cycle 25 could be made.