Premium
Geomagnetic activity and the solar wind during the Maunder Minimum
Author(s) -
Cliver Edward W.,
Boriakoff Valentín,
Bounar Khaled H.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl00500
Subject(s) - earth's magnetic field , solar wind , interplanetary magnetic field , atmospheric sciences , sunspot , solar minimum , solar maximum , solar cycle 23 , physics , solar cycle , magnetic field , quantum mechanics
We used a strong (r = 0.96) correlation between 11‐year averages of sunspot number (SSN) and the geomagnetic aa index to infer that the mean level of geomagnetic activity during the Maunder Minimum (1645–1715) was approximately a third of that observed for recent solar cycles (∼7 nT vs. ∼24 nT). We determined the variation of 11‐year averages of solar wind speed (v) and the southward component of the interplanetary magnetic field (B s ) with cycle‐averaged SSN for the two most recent cycles and also compared cycle‐averaged variations of v²B s and aa for the same interval. We then extrapolated these observed solar wind variations to Maunder Minimum conditions (mean SSN of ∼ 2 and mean aa value of ∼ 7 nT) to deduce that, on average, the solar wind during that period was somewhat slower (v = 340 ± 50 km s −1 ), and the interplanetary magnetic field much smoother (B s = 0.3±0.1 nT), than at present (∼ 440 km s −1 and ∼ 1.2 nT). Various lines of evidence (including 10 Be data) suggest that, despite the virtual absence of sunspots that characterized the Maunder Minimum, the 11‐year geomagnetic (solar wind) cycle persisted throughout this period.