White elliptical light above lightning storm 6/9-10/2013 (Sacramento area)

I'm reporting on behalf of my wife who saw a luminous event on the night of June 9th into the 10th, 2013 (sorry, no pictures). Firstly, I am writing in hopes that others in the Sacramento valley/foothills saw this event as well and will corroborate it in their own words. Secondly, I am asking for the knowledgeable persons in the ATS community for their opinions as to what it was.

I'm sure those in California remember the 108 degree scorcher we had on Saturday (8th), well at least here in the valley and foothills. And I'm sure you remember the much cooler and slightly windy day we had on Sunday. There was talk that we may be getting rain on Monday but we also got a brilliant lightning storm late on Sunday night. Unfortunately I missed it, but my wife watched some of it and saw a very amazing thing!

About 12:30ish, while looking Southwestward from our back deck here in Placer county she watched the lightning, which was between us and Sacramento. During the storm she saw a wide elliptical glowing light appear and hang in the sky above the stormclouds. The solid light was mostly white in color with an aura of blue. The width of the ellipse was about 5 thumbnails across if you were to hold your arm out as far as you could. The event sustained for at least 15 minutes or so, until she went in for the night. It was about half as bright as the moon. Also, not much thunder was heard at all. At first she jokingly thought that "the mothership had come" . But watching it longer she wondered if it was a cloud. But it didn't seem like a cloud at all; It was glowing.

I'm no weather expert so I looked up transient luminous events (TLEs, or upper atmospheric lightning). I showed her pics from wiki for comparison. She said it was like the ELVES but that it was a solid light, not a halo. And even if what she saw was a blue jet or a funny colored sprite it lasted 15+minutes, not 1 millisecond. On reading about ELVES i got to this part...

ELVES is a whimsical acronym for Emissions of Light and Very Low Frequency Perturbations due to Electromagnetic Pulse Sources.[18] This refers to the process by which the light is generated; the excitation of nitrogen molecules due to electron collisions (the electrons possibly having been energized by the electromagnetic pulse caused by a discharge from an underlying thunderstorm).

en.wikipedia.org...

My thoughts? There are some key words in there, "electromagnetic pulse sources". A thunderstorm produces a short EM pulse, singular. The duration of normal TLEs, as far as we know, last a millisecond or two. So what things could lead to a sustained event? Something that produces sustained rhythmic EM pulses, perhaps? What things can produce sustained rhythmic EM pulses? Hmmm...

Then again, maybe it was just an illuminated lenticular cloud hanging over the lightning clouds. Can they do that?

Thanks in advance for the input!