| 词条 | Solar cycle 21 |
| 释义 |
|image=Noaa44sunhalpha19800428.png |caption=The Sun, recorded at the H-alpha wavelength, during solar cycle 21 (28 April 1980). |cycle_num=21 |start_date=March 1976 |end_date=September 1986 |duration=10.5 |max_count=232.9 |max_count_date=December 1979 |min_count=17.8 |spotless_count=273 |prev_name=Solar cycle 20 |next_name=Solar cycle 22 |prev_dates=1964-1976 |next_dates=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 10.5 years, beginning in March 1976 and ending in September 1986. The maximum smoothed sunspot number (SIDC formula) observed during the solar cycle was 232.9, in December 1979, and the starting minimum was 17.8.[3] During the minimum transit from solar cycle 21 to 22, there were a total of 273 days with no sunspots.[4][5][6] The largest solar flare of this cycle (X15) occurred on July 11, 1978.[7] This solar cycle marked the beginning of systematic monitoring of the total solar irradiance from space.[8] See also
References1. ^Kane, R.P. (2002). "Some Implications Using the Group Sunspot Number Reconstruction". Solar Physics 205(2), 383-401. {{Solar cycles}}{{sun-stub}}2. ^{{cite web | title=The Sun: Did You Say the Sun Has Spots? | url=http://www.spacetoday.org/SolSys/Sun/Sunspots.html | publisher=Space Today Online | accessdate=12 August 2010}} 3. ^SIDC Monthly Smoothed Sunspot Number. " " 4. ^Spotless Days. " " 5. ^What's Wrong with the Sun? (Nothing) more information: Spotless Days. "{{cite web |url=https://science.nasa.gov/headlines/y2008/11jul_solarcycleupdate.htm |title=Archived copy |accessdate=2017-07-12 |deadurl=yes |archiveurl=https://web.archive.org/web/20080714032353/https://science.nasa.gov/headlines/y2008/11jul_solarcycleupdate.htm |archivedate=2008-07-14 |df= }}" 6. ^Solaemon's Spotless Days Page. " " 7. ^{{cite web|url=http://www.spaceweather.com/solarflares/topflares.html|title=The Most Powerful Solar Flares ever Recorded|work=spaceweather.com}} 8. ^ Kopp, G. (2016). "Magnitudes and timescales of total solar irradiance variability". JSWSC 6, A30. 1 : Solar cycles |
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