Jaro,
My comments are based on my disbelief that the magnetic field of the earth
has any influence of the radiation we receive from space, whether it is
ionizing or UV.
>>>>> That's a very odd disbelief John.
How then do you account for the enormous difference in radiation dose rates astronauts experience in low earth orbit (on the space station), compared to interplanetary space or even compared to the ground ? (UV certainly doesn't pass through the metal walls).
Or what about the boreal & austral aurora displays ? ....what do you suppose channels the charged particles towards the polar zones and causes their impact to set the night time sky aglow ?
Granted, a large part of radiation dose on earth is shielded off by the thick atmosphere - and varies as a function of altitude - but as the original article I posted said, "sending astronauts beyond the Earth's protective magnetic field will vastly increase their exposure."
Eisenbud & Gesell write in Environmental Radioactivity (4th ed., page 188):
"On entering the earth's magnetic field, some of the primary particles are deflected toward the polar regions, resulting in a somewhat lower radiation flux at the equator. This phenomenon becomes more accentuated with altitudes above a few kilometers, as shown in Fig. 6-11. The difference in the dose rate due to geomagnetic latitude varies from 14% at sea level to 33% at 4360m (Pertsov, 1964)."
Solar flares have the effect of depressing the magnetic field lines so that the pole-vs-equator latitudinal dose rate difference at ground level becomes more like that at high altitude (ie. about double) - that's on top of the much higher radiation levels in the first place.
Another interesting factoid is the 54mSv/y dose rate figure for the ISS -- compared to the old MIR station, which recorded ~40mRem/day (14.6 Rem/y), or 146mSv/y (if I'm doing the conversion correctly).
The ISS is somewhat better shielded compared to MIR, but there is also a difference in the type of orbit each station operates in -- MIR is known to have passed regularly through the South Atlantic Anomaly (SAA), where the magnetic fields do something funny which allows more radiation in... obviously, during the geophysical polar reversal, the whole planet gets to be a real serious anomaly :-)
Jaro
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I was wonder why the comment was made "we're evolved for
radiation" in the context of the article.
By the way, I believe that Mars lacks a magnetic field. Of course, we do
not know if life exist there, so maybe a magnetic field is necessary.
-- John