I searched online for more information on Sally Rogers and the song but had little luck. Her website, though, gave contact information so I sent a message out asking about the origin of the song. To my delight, she replied!
This is what she wrote back:
"I wrote Circle of the Sun on the way to my father's funeral. He had been ill for many years, so when he died at the age of 51 it was a sad relief. As I was driving the three hours from Lansing, MI where I lived to Beulah, MI for the funeral, it was a rotten awful rainy day. But halfway there, the sun broke out, but only in a circle around me. At the same time as my father's death, a good friend was having a baby. The sun, the baby and knowing my dad was finally at peace combined to inspire the song."
Thanks for the information, Sally!