Wikipedia tells me that afterglow is a broad high arch of whitish or rosy light appearing in the sky due to very fine particles of dust suspended in the high regions of the atmosphere.
To me, it’s something else entirely. It’s reliving the memory of what we did together. It’s recreating the atmosphere of our encounter in my head — the way you touched me, the things you said to me, the way you looked at me afterwards. It’s basking in the glory that is you, and it’s the most wonderful feeling ever.