Re: " we're evolved for radiation " - geophysicist on pole revers als

[Muckerheide <muckerheide@attbi.com>]

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 Œmagnetic

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?



Regards, Jim



> When I get a chance, I will crack open my old file of cosmic radiation

> studies that I started to collect 10 years ago.



There's much more data with Google! :-)



> -- John

> John Jacobus, MS

> Certified Health Physicist

> 3050 Traymore Lane

> Bowie, MD  20715-2024

> 

> -----Original Message-----

> From: Muckerheide

> Sent: 11/4/2002 8:46:41 PM

> To: Jacobus, John (NIH/OD/ORS); Jaroslav Franta; radsafe@list.vanderbilt.edu

> Subject: Re: " we're evolved for radiation " - geophysicist on pole revers

> als

> 

> on 11/4/02 1:56 PM, Jacobus, John (NIH/OD/ORS) at jacobusj@ors.od.nih.gov

> wrote:

> 

>> 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,

> 

> How do you "disbelieve" a plain physics fact!?  (It's not even biology!)

> 

> Regards, Jim

> 

>> whether it is

>> ionizing or UV.  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.

> . . .



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