halo, corona, fade
暈 centers on a luminous ring or blurring effect: a halo around the sun or moon, a corona, or the visual softening of a fade. The idea is a surrounding glow that makes edges less distinct.
暈 combines 日 (sun) with 軍, which likely contributes the sound and the idea of something surrounding or encircling, as a halo surrounds the sun. The exact historical development of the component 軍 in this context is uncertain.
The sun 日 sits above 軍, which looks like a vehicle with a covering. Imagine the sun's light being surrounded by a misty military encampment, creating a halo or corona that fades the edges.
For ウン, picture a halo fading in and out like a ghostly 'oon' sound: oon -> ウン, as the corona softly blurs the sun.
dizziness; giddiness; vertigo
blurring (e.g. of an image); blur; gradient; gradation; shading
halo (around the Sun, Moon, etc.); ring; corona
areola mammae (circular area around nipple); areola
solar halo
blur; lack of focus; unsharpness
to be faded; to be hazy; to be blurred; to be out of focus
vertigo; staggers
lunar halo
dizziness; giddiness; vertigo