The counter-argument is equally simple: a sail is a surface. The earth is a sphere. A sphere made of solid rock the size of a sail will be even less moved by a 15 mph breeze than this hypothetical person.
We aren't talking about the earth being blown off course though, just that there is a large amount of energy that was previously unaccounted for and that this energy is large enough to trigger an earth quake at vulnerable parts.
Do the back-of-the-envelope computation of how much energy reaches Earth from a coronal mass ejection and see how well your idea holds up. (a typical flare is 10^16 grams of matter moving at about 450 km/sec)
CMEs reaching earth likely account for a mere fraction of the energy flowing through the global electric circuit at any moment.
Moreover, your suggestion seems to indicate that you’re only considering kinetic energy, which would be a very myopic and reductionist take on these matters.
>The earth is a sphere. A sphere made of solid rock [...]
The earth is NOT a solid rock. It's a very thin layer of rock, floating on top of a pool of magma, itself floating in space. The rock itself flows on all sorts of time scales as well.
A sphere will be forced by the wind, almost the same amount as any other object, regardless of its density or weight.
