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A Recount of Sunspot Groups on Staudach's Drawings
Leif Svalgaard
We have examined the more than 1100 drawings of the solar disk made by the German astronomy amateur Johann Caspar Staudach during 1749-1799 and counted the spots on each image. Usi…
The Effect of Sunspot Weighting
Leif Svalgaard, Marco Cagnotti, Sergio Cortesi
Waldmeier in 1947 introduced a weighting (on a scale from 1 to 5) of the sunspot count made at Zurich and its auxiliary station Locarno, whereby larger spots were counted more than…
Does Building a Relative Sunspot Number Make Sense? A Qualified 'Yes'
Leif Svalgaard
Recent research has demonstrated that the number of sunspots per group ('active region') has been decreasing over the last two or three solar cycles and that the classical Relative…
Reconstruction of Solar Extreme Ultraviolet Flux 1740-2015
Leif Svalgaard
Solar Extreme Ultraviolet (EUV) radiation creates the conducting E-layer of the ionosphere, mainly by photo ionization of molecular Oxygen. Solar heating of the ionosphere creates…
Reconstruction of the Sunspot Group Number: the Backbone Method
Leif Svalgaard, Kennuth H. Schatten
We have reconstructed the sunspot group count, not by comparisons with other reconstructions and correcting those where they were deemed to be deficient, but by a re-assessment of…
Solar Sector Structure
Hugh Hudson, Leif Svalgaard, Iain Hannah
The interplanetary magnetic field near has a characteristic "sector" structure that reflects its polarity relative to the solar direction. Typically we observe large-scale coherenc…