In digital this is often called “glow” or “bloom” effect.
A simple way to simulate this in Krita is by using Filter Masks. Handy about this concept is, that it is driven by the lightness of the image. It is not required to paint the mask (but it is possible to do so, e.g. to fine tune the effect).
The orignal image:
The composition with the filters (overdone here to make the effect obvious):
The cross channel filter controls, in which brightness area of the image the effect should appear and the lens blur adds the additional glow to it.
EDIT:
A similar but more complex way is a “luminosity mask” setup. Krita does not have premade luminosity maks but the tools to create something similar. This solution gives better results and finer control than the more simple solution above and it can be used for any case where you need to drive an image adjustment by its luma values.
