Carrington rotation number
Carrington rotation number(ka -ring-tŏn) A sequential number, introduced by R.C. Carrington, that identifies each solar rotation. Its starting date is 1853 November 9.489 (rotation 1). The number is based on the value of 27.2753 mean solar days that Carrington obtained for the mean synodic rotation period of the Sun from observations of sunspots. This value is equivalent to the Sun having a mean sidereal rotation period of 25.380 mean solar days.
Carrington rotation number[′kar·iŋ·tən rō′tā·shən ‚nəm·bər]
A method of numbering rotations of the sun based on a mean rotation period of sunspots of 27.2753 days, and starting with rotation number 1 on November 9, 1853.