In Star Wars canon, there is no evidence of planetary shields at all. No other passive defences are seen or mentioned.
"The dayside surface of the capital planet was shrouded in smoke from a million fires touched off by meteorite impacts of ship fragments; far too many had fallen to be tracked and destroyed by the planet's surface-defense umbrella. The nightside's sheet of artificial lights faded behind the red-white glow from craters of burning steel; each impact left a caldera of unimaginable death. [...]
Now one last fragmentary ship screamed into the atmosphere, coming in too fast, too steep, pieces breaking off to spread apart and stream their own contrails of superheated vapor; banks of turbolasers on the surface-defense towers isolated their signature, and starfighters whipped onto interception courses to thin out whatever fragments the SD towers might miss [...] "You have to stand down the surface-defense system, sir! It's General Kenobi!" Needa insisted."
General Veers states that there is "force field protecting an area of sixth planet of Hoth system". I got initially confused due to article (English is not my first language) but article an means that only small portion of it is covered.
Fact with most canon policies is that newer release superceds older release, and it is explicitly stated to be case with Star Wars canon.
Which means than relevant screencaps (taken from st-vs-sw.net) are these:
As you can see, there is no evidence of shield at all. All glow present is produced by superlaser heating up planet itself, and glowth being reflected by atmosphere (similar in way our sky on Earth is blue due to atmosphere reflecting/refracting light).
In RotJ novelization we have mention that "shield encompassed them both". However, preface clearly states that "the view-screen depicted the battle station itself, the moon Endor, and a web of energy -- the deflector shield -- emanating from the green moon, encompassing the Death Star." Also, we saw Rebel display in movie:
This means that passage in RotS novelization describing planetary shield not only contradicts itself, but also contradicts higher canon, and is thus invalid.
