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solar flare - can it erase hard drives?



 
 
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  #12  
Old November 8th 03, 01:14 AM
Henry Spencer
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Default solar flare - can it erase hard drives?

In article ,
John Savage wrote:
Also - those X-rays can't reach the ground - Earth's atmosphere is
equivalent of roughly 10 meters of water...


Curious. So if I sunbaked on the bottom of a 1 metre deep swimming pool,
(with a suitable snorkle) I should expect to get sunburnt almost as
severely as when lying on the deck (if we can disregard for the moment
the not insignificant reflection at the air-water interface)?


No, these are two different issues.

To stop X-rays, you basically need mass. Most any kind of mass is as good
as any other kind; essentially nothing is transparent to X-rays. So that
extra 1m of water does not add very much more shielding against X-rays.

But solar X-rays aren't what give you sunburn. Sunburn comes from
short-wavelength ultraviolet.

Stopping short UV is a different problem. Things that are opaque to it
are very very opaque to it; you need only quite a small thickness of such
a material. Normal air is quite transparent to it, so almost all of that
10t/m^2 of air makes no useful contribution here. Ozone is quite opaque
to it, so the traces of ozone found in the lower stratosphere cut out a
lot of it, even though they are a negligible fraction of the atmosphere's
mass. Small thicknesses of water, glass, or even light clothing will
block the remainder completely.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #13  
Old November 9th 03, 12:50 AM
Anders Eklöf
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Default solar flare - can it erase hard drives?

Henry Spencer wrote:

In article ,
John Savage wrote:
Also - those X-rays can't reach the ground - Earth's atmosphere is
equivalent of roughly 10 meters of water...


Curious. So if I sunbaked on the bottom of a 1 metre deep swimming pool,
(with a suitable snorkle) I should expect to get sunburnt almost as
severely as when lying on the deck (if we can disregard for the moment
the not insignificant reflection at the air-water interface)?


No, these are two different issues.

To stop X-rays, you basically need mass. Most any kind of mass is as good
as any other kind; essentially nothing is transparent to X-rays. So that
extra 1m of water does not add very much more shielding against X-rays.


Actually - 1 meter of water roughly reduces hard x-rays by a factor of 5
to 10 depending on energy. Of course, since virtually no solar x-rays
reach ground level it doesn't make a lot of a difference on those ...

But OTOH as you mention, sunbaking is about UV, not x-rays ...
  #14  
Old November 9th 03, 09:22 PM
Brian Gaff
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Default solar flare - can it erase hard drives?


"Mad Scientist" wrote in message
om...
| I was wondering if someone could put to rest this question:
|
| Can the electromagnetic radiation from this solar flare erase hard
| disks or other magnetic media?
Only if your system unit happens to be a couple of million miles nearer the
sun, in space, I'd imagine.

Of course, if the power surge due to the magnetic storm wrecks your puter,
then yes....:-)

Brian

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graphics are great, but the blind can't hear them
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  #15  
Old November 10th 03, 03:57 AM
Henry Spencer
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Default solar flare - can it erase hard drives?

In article ,
=?ISO-8859-1?Q?Anders_Ekl=F6f?= wrote:
To stop X-rays, you basically need mass. Most any kind of mass is as good
as any other kind; essentially nothing is transparent to X-rays. So that
extra 1m of water does not add very much more shielding against X-rays.


Actually - 1 meter of water roughly reduces hard x-rays by a factor of 5
to 10 depending on energy.


Notice the word "more" in my statement. :-) Yes, 1m of water will cut
X-rays down a lot... but compared to an atmosphere equivalent to 10m of
water, the improvement from an extra 1m of water is slight.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #16  
Old November 11th 03, 05:22 AM
Keith F. Lynch
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Default solar flare - can it erase hard drives?

Henry Spencer wrote:
To stop X-rays, you basically need mass. Most any kind of mass
is as good as any other kind; essentially nothing is transparent
to X-rays.


No. There's a strong dependency on atomic number. Lead blocks x-rays
much better than the same mass of water does.

(That's why I was working with beryllium many years ago. It makes a
good airtight x-ray window.)
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I always welcome replies to my e-mail, postings, and web pages, but
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  #17  
Old November 11th 03, 05:25 AM
Keith F. Lynch
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Default solar flare - can it erase hard drives?

Henry Spencer wrote:
While it is possible, "easily" is a vast overstatement. Motors
usually don't produce strong external magnetic fields, and magnetic
media are much more robust than people commonly think -- to have any
effect at all, a magnet must be either very strong or very close
(practically touching the media).


I've had diskettes and tapes erased by taking them on the DC Metro.

They remain ok if I'm careful to keep them off the floor of the
trains, and if I pack them surrounded with a few inches of anything.
--
Keith F. Lynch - - http://keithlynch.net/
I always welcome replies to my e-mail, postings, and web pages, but
unsolicited bulk e-mail (spam) is not acceptable. Please do not send me
HTML, "rich text," or attachments, as all such email is discarded unread.
  #18  
Old November 11th 03, 08:10 PM
Anders Eklöf
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Default solar flare - can it erase hard drives?

Keith F. Lynch wrote:

Henry Spencer wrote:
To stop X-rays, you basically need mass. Most any kind of mass
is as good as any other kind; essentially nothing is transparent
to X-rays.


No. There's a strong dependency on atomic number. Lead blocks x-rays
much better than the same mass of water does.


There is also a strong dependancy on photon energy, especially for high
atomic numbers. What you say is true for x-ray tube x-rays, that are
usually in the 20-200 keV range. You possibly worked with even lower
energies if you used beryllium for windows.
Solar x-rays extend into the MeV range, and there the dependency on
atomic number is next to nothing (within a factor of 2).
  #19  
Old November 12th 03, 03:04 PM
Henry Spencer
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Default solar flare - can it erase hard drives?

In article ,
Keith F. Lynch wrote:
While it is possible, "easily" is a vast overstatement. Motors
usually don't produce strong external magnetic fields, and magnetic
media are much more robust than people commonly think...


I've had diskettes and tapes erased by taking them on the DC Metro.


I've never had any trouble with the Toronto subway. Subway cars do have a
*lot* of current running around -- it's amusing to take a compass along on
a subway ride, and watch it spin back and forth as things switch under the
floor.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
 




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