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Post by tomblvd on Aug 12, 2010 14:52:49 GMT -4
From this webpage (http://www.islandone.org/Settlements/MagShield.html):
I don't quite understand this statement. What, specifically, is "omnidirectional". The protons from the solar event (at least the most energetic ones, assuming a large event) should be in the direction of the sun.
Any ideas?
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Jason
Pluto
May all your hits be crits
Posts: 5,579
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Post by Jason on Aug 12, 2010 16:44:44 GMT -4
"Coming from all directions"
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Post by tomblvd on Aug 12, 2010 16:54:46 GMT -4
thanks........a lot.
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Post by ka9q on Aug 12, 2010 17:04:16 GMT -4
I'm not sure why the proton flux should be omnidirectional; I've been exposed to solar physics but I can't say that I know a lot about it. It could be that because the protons (and other charged particles) are spiraling around the interplanetary (i.e., solar) magnetic field lines, they could come at you from directions other than what you expect. But then I'd expect that at any instant they'd come at you in a plane (a geometrical plane, not an airplane), not necessarily all directions at once.
I think it would be important to nail this down, because if the flux really isn't omnidirectional at all times then it would be unnecessary to provide shielding in all directions. If you can predict the direction from which the particles will come by monitoring the local magnetic field, that suggests you might be able to orient an asymmetric shield to do the most good.
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Jason
Pluto
May all your hits be crits
Posts: 5,579
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Post by Jason on Aug 12, 2010 17:37:23 GMT -4
You're welcome.  |
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Post by echnaton on Aug 12, 2010 17:56:49 GMT -4
IIRC, part of the Apollo contingency for solar flare danger was to position the CSM with the nose pointed away from the sun. The idea was that the mass of the fuel would provide significant shielding from particles. That is consistent with an uni-directional particle stream.
Edited per suggestion.
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Post by grmcdorman on Aug 12, 2010 18:32:01 GMT -4
I think you mean inconsistent. Or uni-directional, yes?
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Post by tomblvd on Aug 12, 2010 20:50:04 GMT -4
I think you mean inconsistent. Or uni-directional, yes? You are correct. That statement is inconsistent with know NASA contingency plans (that were, to be honest, less than a-finger-in-a-dike). So I'm wondering if the flux in directions other than the direction of the sun would somehow be less energetic. |
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Post by randombloke on Aug 13, 2010 3:58:59 GMT -4
You are correct. That statement is inconsistent with know NASA contingency plans (that were, to be honest, less than a-finger-in-a-dike). So I'm wondering if the flux in directions other than the direction of the sun would somehow be less energetic. During a flare event? Almost certainly. Even if the nominal flux of the solar system is omni-directional, a flare is going to be coming directly from the sun and isn't stopping for anything. If we may take an analogy; just because a boat turns its bow into the waves in a storm doesn't mean the water behind isn't still wet. |
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Post by JayUtah on Aug 13, 2010 13:24:15 GMT -4
In solar physics we use the terms "isotropic" and "anisotropic" to describe the directional component of any radiation effect. The quiescent proton flux is isotropic (i.e., omnidirectional) but of too low an intensity to matter. Proton flux from an energetic solar event is ruthlessly anisotropic (i.e., directional).
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Post by ka9q on Aug 13, 2010 16:05:02 GMT -4
So do the protons in a major solar event always move radially away from the sun? They're positively charged, so they'll mutually repel each other. They're moving, so they represent an electric current that produces its own magnetic field that will also affect their motion...
I know the basic principles of electromagnetism well enough, but not being a solar physicist I don't know how they translate to the behavior of charged particles streaming out from the sun.
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Post by tomblvd on Aug 13, 2010 16:31:26 GMT -4
Jay, could you please expand on the term "quiescent proton flux"?
(as an aside, only an engineer could come up with the term "ruthlessly anisotropic")
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Post by JayUtah on Aug 14, 2010 1:43:56 GMT -4
So do the protons in a major solar event always move radially away from the sun?They follow magnetic isolines as "flux ropes." The actual trajectories are spiral, and very beautiful. They're positively charged, so they'll mutually repel each other.True, but generally the magnetic field strength of the planetary and stellar bodies outweigh the interaction among the particles themselves.
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Post by ka9q on Aug 14, 2010 3:56:36 GMT -4
They follow magnetic isolines as "flux ropes." The actual trajectories are spiral, and very beautiful. So I take it that if you were caught in this during an interplanetary cruise to Mars, you could put a shield (e.g., fuel, water or oxygen tankage) between you and whatever direction from which the particles appear to arrive? You wouldn't have to be completely surrounded by shielding? If I were in that situation I'm not sure I'd use the word "beautiful" to describe it, except perhaps in an ironic sense. |
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Post by JayUtah on Aug 14, 2010 12:37:09 GMT -4
Yes, the shielding could be directional. The protocol for Apollo was to turn tail to the oncoming particles and let the bulk of the SM act as shielding. The crew had a handheld counter for finding the safest spot in the CM cabin.
No, if I'm in a spacecraft awaiting the onslaught of high-energy solar protons then I might not think that's particularly beautiful. However seen (after appropriate visualization) from the comfort of my office chair on Earth, it is. A lava geyser will kill me much more quickly and effectively than a proton event. It's pretty deadly. That doesn't mean I can't look at video of lava geysers and think it's beautiful. Remember folks, it's just radiation.
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