I think the inverse square law of which you speak actually has very little effect in reducing the radiation dose between concorde altitudes and boeing altitudes.
The reduction is due to the attenuating affect of the thicker layer of atmosphere above the boeing, compared to the concorde.
Of course it is the attenuation of the thicker atmosphere between 60K ft and 40K ft, but the ILS is always working in your favour when dealing with radiation. Although I don't work with active sources as do my Gamma Camera/ Nuclear Medicine colleagues, I have to know about spills and dealing with accidents involving sources. In this the teaching says; 'the only thing better than 8 feet away, is 12 feet away.'
With any radiation, the inverse square law operates. If it is nuclear radiation, you want to be far away from it and each doubling of the distance increases the protection as the square of the distance. If you want an emergency transmission to get to someone who can help, the ISL works against you in exactly the opposite manner.
After reading 777AV8R's post, it looks like CARI-6 is your best bet, because it seems to fold in all the solar stuff I mentioned, but it is still not
measuring, it is educated guessing. Denti points out that my TLD does not measure Cosmic radiation reliably, although I'm not sure why. The crystal registers any ionizing radiation, although does not give information about source or duration, which my old
film badge used to. Progress?
Roger.