h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I'm reading around several journals for researching a guide entry on solar storms, i keep reading references to "hard spectra" and "spectral shapes modeled on (for example) 1972 event."

In context it is evaluating what, in terms of tissue damage and irradiation, which of the hard spectra would be the most damaging to humans in low earth orbits.

What I want to know is this, what does 'hard spectra' and 'spectral shape' mean?

I'm guessing it's to do with the frequency of the radiation ...how..um...the range of energies is distributed amongst the photons if it's nearer towards an x-ray or a gamma ray etc.

Regrettably these papers don't go in much for definition, and google isn't helping so SEx, I turn to you for council.

Well I know that hard X-rays are higher frequency highly damaging X-rays whereas 'soft' X-rays are of lower energy/frequency that will not be so damaging. Soft X-rays are the ones use to image our bodies for example.

I can imagine the same nomenclature being used for UV and gamma-ray radiation too.

Spectral shape is almost certainly exactly what you describe
An event is likely to a fairly specific distribution of frequencies of irradiation being released. This will be reflected in both the range and intensities of released em radation. This will be the 'shape'. Hence an unknown event or observation that has a very similar or identical spetral shape to something already measured (of known source) will likely be of similar origins.

Excellent.

Cheers Orcus.

And a google search for 'hard x rays' has produced a number of pages with better explanations, including (delightfully) measurements of the difference between a hard and soft x-ray, that I can compare to the estimated doses of the solar flare.