Solar cycle 18 was the eighteenth
solar cycle
The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surfa ...
since 1755, when extensive recording of solar
sunspot
Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sun ...
activity began.
The solar cycle lasted 10.2 years, beginning in February 1944 and ending in April 1954. The maximum
smoothed sunspot number
The Wolf number (also known as the relative sunspot number or Zürich number) is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the Sun.
History
Astronomers have been observing the Sun recordi ...
observed during the solar cycle was 218.7 (May 1947), and the starting minimum was 12.9.
[SIDC Monthly Smoothed Sunspot Number.]
During the minimum transit from solar cycle 18 to 19, there were a total of 446 days with no sunspots.
[Spotless Days.]
[Solaemon's Spotless Days Page.]
Cycle 18 was characterized by "giant" sunspots.
The recording of the 10.7 cm (2800 MHz)
Ionosphere#Solar flux, solar radio flux began partway during this cycle,
and values of the solar flux during this cycle turned out to be particularly high.
See also
*
List of solar cycles Solar cycles are nearly periodic 11-year changes in the Sun's activity that are based on the number of sunspots present on the Sun's surface. The first solar cycle conventionally is said to start in 1755 when Rudolf Wolf began extensive reporting o ...
References
Solar cycles
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