Nitric acid decomposition

I have a problem with the decomposition reaction of Nitric acid($\ce{HNO3}$) by light.
My problem: is that reaction is a redox reaction?
If it is please tell me the oxidation and reduction (balanced) reactions seperately.




Generally, nitric acid is a strong oxidizing agent which get reduce to nitrogen oxides on reacting with metals which act as reducing agent thus forming a redox reaction. But in this case, only nitric acid is involved which get reduced to nitrogen oxides on reaction with air/light. So, this may be called oxidation reaction where nitric acid gets oxidized. From wikipedia article of [nitric acid](https://en.m.wikipedia.org/wiki/Nitric_acid):



> 
> **Nitric acid is subject to thermal or light decomposition and for this reason it was often stored in brown glass bottles:**
> 
> 
> $$\ce{ 4 HN^{V}O3 → 2 H2O + 4 N^{IV}O2 + O2}$$
> 
> 
> This reaction may give rise to some non-negligible variations in the
>  vapor pressure above the liquid because the nitrogen oxides produced
>  dissolve partly or completely in the acid.
> 
> 
> The nitrogen dioxide ($\ce{NO2}$) remains dissolved in the nitric acid
>  coloring it yellow or even red at higher temperatures. While the pure
>  acid tends to give off white fumes when exposed to air, acid with
>  dissolved nitrogen dioxide gives off reddish-brown vapors, leading to
>  the common name "red fuming acid" or "fuming nitric acid" – the most
>  concentrated form of nitric acid at Standard Temperature and
>  Pressure (STP). Nitrogen oxides ($\ce{NO\_x}$) are soluble in nitric
>  acid.
> 
> 
> 


There are some old papers([here](http://pubs.acs.org/doi/abs/10.1021/j150530a004) and [here](http://pubs.rsc.org/en/Content/ArticleLanding/1912/CT/ct9120100131)) which discuss the mechanism of nitric acid decomposition. Give a quick read on the papers and you will understand the mechanism of the reaction.


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