There’s a variety of methods that I’ve seen used in games, and it really depends on which one works best for the visual effect you’re looking for.
I’ve seen camera-facing sprites (usually rotated along a specific axis so it always matches the character’s shape) spawned at the different bones in some games, and inverted normal “aura” models in some others (DC Universe Online does this for their auras for an UE related example). There’s some that rely on other types of aura meshes or particles too, but it really depends on the specific effect you want.
Judging by the picture you posted, it’s probably a series of animated sprite images spawned for each desired bone and along the length of the weapon, but that’s just a best guess from what I can see in that screenshot.