Adding a radial force component near the feet of your character and firing it upon landing may be feasible for your application. Just be careful that this doesn’t overlap with geometry as it will, by default, only push actors that are not blocked on the visibility channel. You could also perform a sphere trace with the same radius, and whomever is within the sphere trace (which I would perform just before the firing of the impulse) you can call an RPC for a “stunned” animation, or whatever you choose to do. In that circumstance I’d personally have the RPC simply flag the character with an “isStunned” boolean, and handle the animation in your anim BP, and finally handle setting “isStunned” to false after a short amount of time. Personally, I’d avoid delays here as well, and simply count frame delta until your ideal time has elapsed.
Impulse isn’t as reliable as other solutions, however. A more ideal approach might be to simply conduct the sphere trace upon landing, call the RPC(s) on any actor(s) hit by the trace, and have a root motion “stunned”/“knocked back” montage fire off. Then you have complete control, via your animation(s), of what happens. With impulse, some wild things can happen which is typically great for a rocket launcher, but not so great for knocking back enemies in a consistent manner.
What I personally REALLY like about montages, is that they can be interrupted and you can account for that. If you knock someone off of a cliff, for example, your falling animation (if it already exists in your Anim BP and is setup properly) will interrupt the montage. This looks very nice, and would prevent a glitchy-looking “I’m walking back in a dazed state” animation in mid-air (or while falling).