Solar cycle 21

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Solar cycle 21
The Sun, recorded at the H-alpha wavelength, during solar cycle 21 (28 April 1980).
Sunspot Data
Start date June 1976
End date September 1986
Duration (years) 10.3
Max count 164.5
Max count month December 1979
Min count 12.3
Spotless days 273
Cycle chronology
Previous cycle Solar cycle 20 (1964-1976)
Next cycle Solar cycle 22 (1986-1996)


Solar cycle 21 was the 21st solar cycle since 1755, when extensive recording of solar sunspot activity began.[1][2] The solar cycle lasted 10.3 years, beginning in June 1976 and ending in September 1986. The maximum smoothed sunspot number (monthly number of sunspots averaged over a twelve-month period) observed during the solar cycle was 164.5, in December 1979 (the second-highest peak on record), and the minimum was 12.3.[3] There were a total of 273 days with no sunspots during this cycle.[4][5][6] The largest solar flare of this cycle (X15) occurred on July 11, 1978.[7]

See also[edit]

References[edit]

  1. ^ Kane, R.P. (2002). "Some Implications Using the Group Sunspot Number Reconstruction". Solar Physics 205(2), 383-401.
  2. ^ "The Sun: Did You Say the Sun Has Spots?". Space Today Online. Retrieved 12 August 2010. 
  3. ^ SIDC Monthly Smoothed Sunspot Number. "[1]"
  4. ^ Spotless Days. "[2]"
  5. ^ What's Wrong with the Sun? (Nothing) more information: Spotless Days. "[3]"
  6. ^ Solaemon's Spotless Days Page. "[4]"
  7. ^ http://www.spaceweather.com/solarflares/topflares.html