Letter to the Editor

Was the unusual solar cycle at the end of the XVIII century a result of phase asynchronization?

Institute of Physics, Saint-Petersburg State University, Russia e-mail: [ned;ponyavin]@geo.phys.spbu.ru

Received: 19 April 2007
Accepted: 22 May 2007

Abstract

Aims.The problem of the unusual sunspot cycle in 1784–1799 is considered. Why was the length of the 4th solar cycle exceptionally large? Was it really composed of two shorter cycles? Resolving this puzzle seems to be very important for modern dynamo theories trying to explain the solar cyclicity.

Methods.We propose a possible scenario for the solar activity behavior during the 4th solar cycle. Analogies with the phase asynchronization observed at the time of the 20th solar cycle are presented.

Results.We suggest that the length of the 4th solar cycle can be explained by outstanding phase asynchrony between Northern and Southern hemispheric activities reaching a delay up to 4.5 years. The main effect of such asynchronization results in strong North-South asymmetry during the course of the ascending phase of the solar cycle 4.