Originally posted by Baack
Unless the glow unavoidably indicates some sort of waste heat dump or venting method, perhaps due to the vast amounts of energy these craft might
Any theories out there? Thanks in advance.
Well, the British Ministry of Defence report on UFOs ("UAPs") released on their website today says the glow is a naturally occuring plasma.
Other theories have included:
(a) Paul Hill states that there is an "illuminated and
illuminating sheath of atmosphere [around UFOs which] is a
sheath of ionized and excited air molecules often called a
plasma" which Hill asserts is caused by a "power-plant-
connected, ionizing, wave type radiation from the UFO" 
(b) James M Campbell has written a book which discusses reports
indicating the presence of plasma, contending that this plasma
is the result of "the propulsion system of UFOs [involving] the
emission of microwave energy". 
(c) A different connection between vehicles and plasma was put
forward by Stanton T Friedman in his written statement evidence
to the Roush hearing. He referred to publications relating to
"interactions between vehicles and plasmas", stating that "there
is a body of technology which I have studied and which leads me
to believe that an entirely new approach to high speed air and
space propulsion could be developed using the interactions
between magnetic and electric fields with electrically
conducting fluids adjacent to the vehicles to produce thrust or
lift and reduce or eliminate such other hypersonic flight
problems as drag, sonic boom, heating, etc". 
 Hill, Paul R in his "Unconventional Flying Objects : A
Scientific Analysis" (1995) at 53-54 (in Section III) of the
Hampton Roads softcover edition.
 Campbell, James M in Chapters 3 and 6 of his book
"Ufology". The text of the relevant book is available online at:
 Friedman, Stanton J in the Roush Hearing (the U.S. House of
Representatives Committee on Science and Astronautics "Symposium
on Unidentified Flying Objects" on 1968.0729) at page 217 of the
transcript of the Ninetieth Congress, Second Session, Number 7.
Edited and annotated transcript presented by Fuller, John in his
"Aliens in the Skies" (1969). Complete transcript available free
online at the following links:
Hope this helps you.
Of course, the "glow" could simply be the lights from aircraft etc...
All the best,