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The solar constant includes radiation over the entire electromagnetic spectrum. It is measured by satellite as being 1.361 kilo watts per square meter (kW/m 2) at solar minimum (the time in the 11-year solar cycle when the number of sunspots is minimal) and approximately 0.1% greater (roughly 1.362 kW/m 2) at solar maximum. [1]
Total solar irradiance (TSI) [21] changes slowly on decadal and longer timescales. The variation during solar cycle 21 was about 0.1% (peak-to-peak). [22] In contrast to older reconstructions, [23] most recent TSI reconstructions point to an increase of only about 0.05% to 0.1% between the 17th century Maunder Minimum and the present.
The updated figure (right) shows the variations and contrasts solar cycles 14 and 24, a century apart, that are quite similar in all solar activity measures (in fact cycle 24 is slightly less active than cycle 14 on average), yet the global mean air surface temperature is more than 1 degree Celsius higher for cycle 24 than cycle 14, showing the ...
The solar flux unit (sfu) is a convenient measure of spectral flux density often used in solar radio observations, such as the F10.7 solar activity index: [1] 1 sfu = 10 4 Jy = 10 −22 W⋅m −2 ⋅Hz −1 = 10 −19 erg⋅s −1 ⋅cm −2 ⋅Hz −1 .
Taken on 20 October 1968 from Apollo 7. ... (1.01671033 AU) squared should be approximately 0.935338. ... The solar constant is a measure of flux density, ...
As at Feb 20, 2025, solar cycle 25 is averaging 37% more spots per day than solar cycle 24 at the same point in the cycle (Feb 20, 2014). Year 1 of SC25 (Dec 2019 to Nov 2020) averaged 101% more spots per day than year 1 of SC24. Year 2 of SC25 (Dec 2020 to Nov 2021) averaged 7% more spots per day than year 2 of SC24.
Radiant flux emitted, reflected, transmitted or received, per unit solid angle. This is a directional quantity. Spectral intensity: I e,Ω,ν [nb 3] watt per steradian per hertz W⋅sr −1 ⋅Hz −1: M⋅L 2 ⋅T −2: Radiant intensity per unit frequency or wavelength. The latter is commonly measured in W⋅sr −1 ⋅nm −1. This is a ...
The 2003 Halloween solar storms had a peak Dst index of −383 nT, although a second storm on 20 November 2003 reached −422 nT while not reaching G5-class. [ 16 ] [ 17 ] The March 1989 geomagnetic storm had a peak Dst index of −589 nT, [ 18 ] while the May 1921 geomagnetic storm has been estimated to have had a peak Dst index of −907 ± ...