Wolf number

[woo lf; French vawlf]
noun Astronomy.
  1. a number indicating the degree of sunspot activity on the sun as a factor of observer idiosyncrasies, the number of sunspot groups, and the number of individual sunspots.

Origin of Wolf number

1975–80; after Rudolf Wolf (1816–93), Swiss astronomer
Also called relative sunspot number, sunspot number.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018