CS Forum: Prof. Ilya Usoskin
Title: The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets.
Place: Odeion, TUAS, Otaniementie 17
Host: Visiting Dr Maarit Käpylä
Abstract
Aims: Although the time of the Maunder minimum (1645–1715) is widely known as a period of extremely low solar activity, it is still being debated whether solar activity during that period might have been moderate or even higher than the current solar cycle #24. We have revisited all existing evidence and datasets, both direct and indirect, to assess the level of solar activity during the Maunder minimum.
Methods: We discuss the East Asian naked-eye sunspot observations, the telescopic solar observations, the fraction of sunspot activedays, the latitudinal extent of sunspot positions, auroral sightings at high latitudes, cosmogenic radionuclide data as well as solar eclipse observations for that period. We also consider peculiar features of the Sun (very strong hemispheric asymmetry of the sunspot location, unusual differential rotation and the lack of the K-corona) that imply a special mode of solar activity during the Maunder minimum.
Results: The level of solar activity during the Maunder minimum is reassessed on the basis of all available datasets.
Conclusions: We conclude that solar activity was indeed at an exceptionally low level during the Maunder minimum. Although the exact level is still unclear, it was definitely lower than during the Dalton minimum of around 1800 and significantly below that of the current solar cycle #24. Claims of a moderate-to-high level of solar activity during the Maunder minimum are rejected with a high confidence level.
Bio
In 1988 Ilya graduated M.Sc. in Physics from the Leningrad Polytechnics (presently St.Petersburg State Technical University). As a researcher at the A.F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences (St. Petersburg), he obtained his PhD in Astrophysics in 1995, on the topic of solar energetic particles. During 1997-1999 he held a postdoc at the INFN (Institute Nationale di Fisica Nucleare) in Milano, working with a space-borne cosmic ray spectrometer AMS (Alpha Magnetic Spectrometer). Since 2000 he has been at the University of Oulu as head of Oulu Cosmic Ray Station. From 2012 he has been a professor at the Faculty of Sciences of the University of Oulu, then from 2014 vice-director of the ReSoLVE Centre of Excellence. His main research topics: cosmic rays (experimental issues, heliospheric modulation, atmospheric effect of cosmic rays), solar physics (long-term solar activity variability, and solar energetic particles).