Doctor Solar, Man of the Atom #1 ( October 1962) debuted from the fledgling Gold Key imprint created out of the split between Dell and Western Publishing, basically a move that originated when when Western switched to in-house publishing rather than packaging content for branding and distribution by its business partner, Dell Comics.
Raymond Solar, from the beginning, was a character that bucked several cliched superhero conventions of the era.
One, his origin made him out to be a fairly tragic figure. Irradiated in an "atomic accident", Solar gained energy manipulation abilities and several other typical more than human attributes, but as a result of his origin, he basically became a walking atomic pile, forced into a life of solitude because of the enormous amounts of radiation he was prone to give off.
Second, he lived this tragic Hulk-like existence for the first 5 issues of his book...with matching green skin, to boot...that is, until his fifth issue, where he finally received his official red union suit and basically for the rest of his title's run (which lasted about 30 plus issues spread out of two decades) became a typical superhero battling giant robots, dinosaurs, and the occasional evil scientist.
Third, his origin sequence itself is kinda long in the tooth compare to the typical "8 pages and yer a hero" origin story that was the norm of the day, the transition from hip young scientist (you can tell he's cool because he's constantly wearing sunglasses), to radiation victim to full blown costumed do-gooder taking the aforementioned 5 issues to finally bear fruit....
Below is a download link for scans of my copies of the first five issues of Solar's Silver Age Gold Key incarnation...
Download Link (Hosted by Megaupload)
Once you've had a chance to check out the good Doc's Silver Age origin, hopefully we'll be able to compare and contrast it to his 1990s incarnation's debut story....
Solar: The Valiant Years
Now, I was a huge fan of Valiant Comics and their tight little shared universe continuity during the earlier part of their publishing existence. I dare anyone to find a tighter continuity than those books possessed. Everything was nice and neat, everything was connected, and in ways that actually IMO made sense.
Valiant's origin of Solar was a trippy little deal, that dealt with time travel, alternate universe's and the possibilities of what might happen if a person actually did come into possession of god-like powers and,....well....actually became God. Plus, it was written by Jim Shooter (the man who practically reinvented Marvel in the 1980s, putting it on the road to multimedia giant that it is today) and illustrated by Barry Windsor-Smith....
The Valiant origin went as a far as acknowledging the Gold Key version of the character, who much like in our reality, is a fictional comic book character, as evidenced in the page below (from Solar, Man of the Atom #2 October 1991)
Solar: Alpha & Omega Download Link (Hosted by Megaupload)