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GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 24, 2183, doi:10.1029/2002GL015640, 2002

Lost sunspot cycle in the beginning of Dalton minimum: New evidence and consequences

I. G. Usoskin

Sodankylä Geophysical Observatory, University of Oulu, Finland


K. Mursula

Department of Physical Sciences, University of Oulu, Finland


G. A. Kovaltsov

Ioffe Physical-Technical Institute, St.Petersburg, Russia


Abstract

We have recently suggested that one solar cycle was lost in the beginning of the Dalton minimum during 1790s [ Usoskin et al., 2001 ]. Earlier, this cycle has been combined with the preceding activity to form the exceptionally long solar cycle 4 in 1784-1799 with an irregular phase evolution. Here we show that historical data of auroral occurrence provide independent evidence for the existence of the new cycle. Using a heliospheric model we demonstrate that 10Be or any other cosmogenic isotope data do not exclude the possibility of a new cycle. We also discuss the other implications of the new cycle for solar activity, in particular the cycle length distribution and the Waldmeier relation between the cycle amplitude and the length of the ascending and descending phase. Including the new cycle also restores the Gnevyshev-Ohl rule of cycle pairing and removes the phase catastrophe in the beginning of the Dalton minimum.

Published 24 December 2002.

Index Terms: 7536 Solar Physics, Astrophysics, and Astronomy: Solar activity cycle (2162); 1650 Global Change: Solar variability; 2162 Interplanetary Physics: Solar cycle variations (7536).

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Citation: Usoskin, I. G., K. Mursula, and G. A. Kovaltsov (2002), Lost sunspot cycle in the beginning of Dalton minimum: New evidence and consequences, Geophys. Res. Lett., 29(24), 2183, doi:10.1029/2002GL015640.