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Re: " we're evolved for radiation " - geophysicist on pole reversals
John and other Radsafer
For more information you can look at NCRP Report No. 132 "Radiation
Protection Guidance for Activities in Low-Earch Orbit".
_____________
John R Johnson,
PhD idias@interchange.ubc.ca
----- Original Message -----
From: "Jacobus, John (NIH/OD/ORS)" <jacobusj@ors.od.nih.gov>
To: <radsafe@list.vanderbilt.edu>
Sent: Tuesday, November 05, 2002 11:03 AM
It is the atmosphere that protects the earth from the high-LET particles
that the astronauts are exposed to. NCRP report 98 is a good reference on
exposure in space.
Hove a good week.
-- John
John Jacobus, MS
Certified Health Physicist
3050 Traymore Lane
Bowie, MD 20715-2024
E-mail: jenday1@email.msn.com (H)
-----Original Message-----
From: Muckerheide [mailto:muckerheide@attbi.com]
Sent: Tuesday, November 05, 2002 1:36 AM
To: Jacobus, John (NIH/OD/ORS); Jaroslav Franta;
radsafe@list.vanderbilt.edu
Subject: Re: " we're evolved for radiation " - geophysicist on pole re
vers als
on 11/4/02 11:11 PM, Jacobus, John (NIH/OD/ORS) at jacobusj@ors.od.nih.gov
wrote:
> Jim,
> The magnetic fields shield the earth for the electron and protrons that
are
> ejected from the sun. However, they do not protect us from the high
energy
> cosmic radiation that penetrates into the atmosphere. (It is one of those
> physics things.) What plain physics fact were you talking about?
John,
A little 'physics thing' help re space radiation, e.g.:
"1.3.1 Geomagnetic Shielding
"For cosmic rays to reach a spacecraft in Earth orbit, they must penetrate
the Earthıs magnetic field. Since they are moving, charged particles, they
will tend to be deflected by the magnetic field. However, this tendency is
opposed by the energy of the particles as they move at high velocity towards
the Earth. A particleıs penetrating ability is determined by its momentum
divided by its charge, and this quotient is referred to as its OEmagnetic
rigidityı. A cosmic ray will require a minimum magnetic rigidity to reach
each point within the Earthıs magnetic field. Particles below the minimum
will be deflected and this minimum is called the geomagnetic cutoff value.
As mentioned earlier, geomagnetic disturbances may affect the cutoff,
usually lowering it.
"The cutoff value falls to zero at the edges of the magnetosphere and at the
Earthıs magnetic poles. Since the cosmic ray flux is highest at low
energies, a satellite in Earth orbit will be protected to some extent from
cosmic rays by the magnetic field..."
Not to mention the earth's surface!
http://www.estec.esa.nl/gpqwww/paso/padocs/refer/uecsre/handbook.htm
Maybe you can "undisbelieve" now?
. . .
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