noun which may take the genitive case particle 'no', noun
full of vigor and vitality; in the ascendant
A yojijukugo describing a person or thing brimming with energy and on the rise, like the morning sun climbing into the sky. Often used in formal or literary contexts.
His momentum is truly like the rising sun—full of vigor and on the ascent.
He takes on the new venture with the spirit of a rising sun, full of vitality.
旭日 means 'rising sun' and is a component of this yojijukugo, but it lacks the full idiomatic sense of vigorous ascent.
勢い盛ん is a more common, everyday expression for 'full of vigor' or 'in full swing', while 旭日昇天 is a formal, literary yojijukugo.
A yojijukugo composed of 旭日 (rising sun) and 昇天 (ascending to heaven), evoking the image of the sun climbing vigorously into the sky. The exact origin is uncertain, but it follows a common pattern of four-character idioms using natural imagery to express abstract qualities.