Solar cycle 21
| 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
References
- ^ Kane, R.P. (2002). "Some Implications Using the Group Sunspot Number Reconstruction". Solar Physics 205(2), 383-401.
- ^ "The Sun: Did You Say the Sun Has Spots?". Space Today Online. Retrieved 12 August 2010.
- ^ SIDC Monthly Smoothed Sunspot Number. "[1]"
- ^ Spotless Days. "[2]"
- ^ What's Wrong with the Sun? (Nothing) more information: Spotless Days. "[3]"
- ^ Solaemon's Spotless Days Page. "[4]"
- ^ "The Most Powerful Solar Flares ever Recorded". spaceweather.com.
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