(صورة توضيحية فقط)
The solar constant is the mean solar electromagnetic radiation per unit area measured at the top of Earth’s atmosphere, perpendicular to the rays. Its value is approximately 1361 watts per square meter ([latex]W/m^2[/latex]). This figure varies slightly with solar activity and Earth’s orbital distance, but serves as a fundamental baseline for climate science, satellite design, and renewable energy calculations.
The solar constant represents the total solar irradiance (TSI) at a distance of one astronomical unit (AU) from the Sun. While termed a ‘constant’, its value is not perfectly fixed. It fluctuates by about 0.1% over the 11-year sunspot cycle and has longer-term variations. These small changes are significant for Earth’s climate system. Early measurements, like those by Claude Pouillet in 1838 using his pyrheliometer, were crucial first steps but were inaccurate due to not fully accounting for atmospheric absorption. It was only with the advent of satellite-based radiometers in the late 20th century that a precise and continuous measurement of the solar constant became possible. The accepted value of approximately 1361 W/m² is a cornerstone for calculating Earth’s energy balance, determining the equilibrium temperature of the planet, and designing systems that operate in space. For instance, engineers must know this value precisely to design thermal control systems for satellites to prevent overheating or freezing, and to calculate the power output of their solar arrays. It is the fundamental input for global climate models that simulate Earth’s past and future climate.
ملحوظة: في حين أنه يمثل إجمالي الطاقة التي تتلقاها الأرض من الشمس ككل، بجميع الطرق الكهرومغناطيسية، فإنه ليس القيمة التي يمكن استخدامها بشكل مباشر للألواح الشمسية الموجودة على الأرض.
الثابت الشمسي
(إذا كان التاريخ غير معروف أو غير ذي صلة، على سبيل المثال "ميكانيكا الموائع"، يتم توفير تقدير تقريبي لظهوره الملحوظ)
الصور والتنزيلات بالحجم الكامل متاحة فقط، ومجانية تمامًا، للأعضاء المسجلين.
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