An alleged "4 second" time gap is disputable. We frequently hear about JFK Assassination eyewitnesses being in shock or just standing in place wondering what exactly has gone down with the JFK Limo speeding away, SA Hill mounting the trunk, etc. The Darnell image shows people Streaming into the TSBD. Time has obviously passed. Getting back to the actual figure, I think a woman wearing Short White Gloves ending at the Wrists is another possibility for the Illumination. She could be holding a Coke Bottle or a Cup of Joe, but short White Gloves could be the source for the Illumination/Glow.
if I'm understanding you correctly it highlights how poor your contribution to this particular aspect of things has been. The point you raised about the time difference between the two images in the Gif I posted is totally valid. If the gap between the two images is too long my proposal of the images showing someone lighting a cigarette fails. It's a good test of the proposal.
Here's where things start to fall down. I'm talking about the time difference between these two images from Wiegman:

I used the Wiegman film to locate these two frames and roughly measure the difference between them which turned out to be approximately 4 seconds, a perfectly reasonable time to light a cigarette. But you disputed this 'alleged' timing arguing "Time has obviously passed" because of the "people Streaming into the TSBD". I looked at the images but couldn't understand what you meant. Then it dawned on me -
you're talking about the time difference between the Wiegman and Darnell images!!!WTF
And now you're just making the first thing that comes into your head about what the light source might be. White gloves? Really? Why is it glowing? Why aren't both hands glowing? Why has it stopped glowing in the Darnell clip?
Maybe it's Michael Jackson with a single sequined glove on?
Doesn't it look like someone lighting a cigarette and blowing out smoke?