Earthed

What is the equation to calculate solar flux at a certain planet?

What is the equation to calculate solar flux at a certain planet?

Public Comments

1. Divide the solar luminosity (the total power output of the sun, L=3.827 * 10^26 W) by the surface area of a sphere that has a radius (R) equal to the distance of the planet from the sun.
   
   
   
   Flux(R) = (3.827*10^26 W)/(4*pi*R^2 m^2)
   
   
   
   If you express R in meters, then the flux will be in watts/m^2.
   
   
   
   Obviously, this does not account for absorption/scattering by the planet's atmosphere (if it has one) and so gives the flux at the top of the planet's atmosphere (if it has one), not the surface (if it has one of these!).
2. Per unit area:
   
   Inverse-Square Law S = So (ro/r)2
   
   S = Solar Flux received at the planet
   
   Where:
   
   So= Solar Flux at Earth =1370 W/m2
   
   r = distance of planet from the sun
   
   ro = distance of Earth from the Sun= 1 A.U.
   
   
   
   To find the total, multiply by the cross sectional area of the planet --
   
   pi r^2
   
   Make sure you use the same units and check that this is the flux constant you want.