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Solar cycle 25 is the current solar cycle, the 25th since 1755, when extensive recording of solar sunspot activity began. It began in December 2019 with a minimum smoothed sunspot number of 1.8. [2] It is expected to continue until about 2030. [3] [4]
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 have started in 1755. The source data are the revised International Sunspot Numbers (ISN v2.0), as available at SILSO. [1]
Solar cycle 23 lasted 11.6 years, beginning in May 1996 and ending in January 2008. The maximum smoothed sunspot number (monthly number of sunspots averaged over a twelve-month period) observed during the solar cycle was 120.8 (March 2000), and the minimum was 1.7. [29] A total of 805 days had no sunspots during this cycle. [30] [31] [32]
Sunspot AR3664 visible on the bottom right part of the Earth-facing side of the sun on May 9, 2024. (NASA/ Solar Dynamics Observatory) Millions of people who went out of their way to find eclipse ...
The aurora is expected to be bright and visible in multiple northern U.S. states Oct. 3 through Oct. 5 as well as from the lower Midwest to Oregon.
Individual sunspots or groups of sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from 16 km (10 mi) [3] to 160,000 km (100,000 mi). [4] Larger sunspots can be visible from Earth without the aid of a telescope. [5]
The Carrington heliographic coordinate system, established by Richard C. Carrington in 1863, rotates with the Sun at a fixed rate based on the observed rotation of low-latitude sunspots. It rotates with a sidereal period of exactly 25.38 days, which corresponds to a mean synodic period of 27.2753 days.
An active region containing a single sunspot or group of sunspots all having the same magnetic polarity. An opposite polarity counterpart is still present, but is weak or not concentrated enough to form sunspots. β: An active region with at least two sunspots or sunspot groups that have opposite magnetic polarity.