bright light, sunlight, dazzling
昱 centers on intense, radiant light: bright sunlight that dazzles or illuminates clearly.
昱 combines 日 (sun) above 立 (stand), suggesting the sun standing high and shining brightly. The exact historical development is uncertain, but the component arrangement visually conveys radiant sunlight.
The sun 日 stands 立 tall in the sky, pouring down dazzling bright light.
For イク, imagine the sun standing so bright that it makes you say 'eek!' (イク) and shield your eyes from the dazzling light.