Do you want to know about solar cycles?  <a href="https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;Solar_cycle" rel="nofollow">https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;Solar_cycle</a><p>There&#x27;s a solar irradiance section that explains:<p>&gt; Solar irradiance varies systematically over the cycle, both in total irradiance and in its relative components (UV vs visible and other frequencies). The solar luminosity is an estimated 0.07 percent brighter during the mid-cycle solar maximum than the terminal solar minimum. Photospheric magnetism appears to be the primary cause (96%) of 1996-2013 TSI variation. The ratio of ultraviolet to visible light varies.