How much of this momentum can get transferred, and at what rate?

Note: Force is the time rate of change of momentum

This momentum transfer will accelerate the stellar wind

One particle, with an effective cross-sectional area of s (cm2) can “catch” the flux of momentum (momentum cm-2 s-1), f/c, at the rate given by

This is the rate at which the particle gains momentum from the photons, which is the radiation force on the particle

Note that another way to see this is that the force, Frad, divided by area over which it is exerted, is a pressure. In other words, momentum flux and pressure are identical.

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