One of the unsolved solar mysteries is the peculiar behaviour around year 1800. The data we have is poor leading to ambiguity on whether a solar sunspot cycle is missing from the record.
Figures from paper. For a legible copy you will need to register and download the PDF.
The lost sunspot cycle: New support from 10Be measurements
C. Karoff, F. Inceoglu, M. F. Knudsen, J. Olsen, A. Fogtmann-Schulz
A&A 575 A77 (2015)
(early preview with registration)
It has been suggested that the shortage in the number of spots on the surface of the Sun between 1790 and 1830, known as the Dalton minimum, contained an extra cycle that was not identified in the original sunspot record by Wolf. Though this cycle was shorter and weaker than the average solar cycle, it shifted the magnetic parity of the solar magnetic field of the earlier cycles. This extra cycle is sometimes referred to as the “lost solar cycle” or “cycle 4b”. Here we reanalyse 10 Be measurements with annual resolution from the North Greenland Ice Core Project in order to investigate if the hypothesis regarding a lost sunspot cycle is supported by these measurements. Specifically, we make use of the fact that the Galactic cosmic rays, responsible for forming 10 Be in the Earth’s atmosphere, are affected differently by the open solar magnetic field during even and odd solar cycles. This enables us to evaluate if the numbering of cycles earlier than cycle 5 is correct. For the evaluation, we use Bayesian analysis, which reveals that the lost sunspot cycle hypothesis is likely to be correct. We also discuss whether this cycle 4b is a real cycle or a phase catastrophe, and what implications this has for our understanding of stellar activity cycles in general.
The authors are cautious. They’ve used Bayesian methods to push hard on the limits of what can be done.
They claim no more than the supposition is supported but do not rule out other explanations.
corresponding to a p-value of 99.82 ± 0.06%, which implies that the lost cycle hypothesis is decisively supported by the 10 Be measurements from the NGRIP ice core.
Though we have shown that the lost cycle hypothesis is decisively supported by the 10Be measurements, there are still a number of explanations that cannot be ruled out.
And go on to discuss some of them.
Post by Tim