Solar Flares Shield Astronauts from Cosmic Rays 135
It doesn't come easy writes "Considering all of the research into better shielding for astronauts, it's interesting to note that solar flares can help shield space travelers from dangerous cosmic rays. From the article: "The crew of the ISS absorbed about 30% fewer cosmic rays than usual [during this last month of high solar activity]," says Frank Cucinotta, NASA's chief radiation health officer at the Johnson Space Center. "The storms actually improved the radiation environment inside the station." Scientists have long known about this phenomenon. It's called a "Forbush decrease," after American physicist Scott E. Forbush, who studied cosmic rays in the 1930s and 40s. So, I guess it would be safer to plan a manned Mars mission to coincide with peak sunspot activity?"
Re:The fantastic four (Score:3, Informative)
NASA source (Score:4, Informative)
Another source:
Strange, but true: Solar flares can be good for astronauts. [nasa.gov]
Re:Mars trip during solar storm (Score:5, Informative)
There may be a decrease in radiation coming from elsewhere, but the ship would still be hammered by high speed Coronal Mass Ejection particles. Radiation sheilding is essential; Bring your polyethylene, in other words.
Re:Danger Level (Score:4, Informative)
Of course, these same cosmic rays will also destroy cells in the brain and fragment DNA, potentially generating damage which could either lead to cancer or lead to genetic problems which could be passed on to future generations.
Although I can't quantify the risk associated with the latter phenomena, knowing that every time I see a little flash I have suffered a small but permanent loss of vision would make space travel less appealing.
Great, but... bone loss still a problem (Score:2, Informative)
A simplistic source, (http://www.factmonster.com/ipka/A0778174.html [factmonster.com]) has this easy to digest quote
"... And because the gravity on Mars is only 38% of Earth's, ways to counteract any damaging effects of the weak gravity on their bodies, such as progressive bone loss and muscle atrophy, will have to be found. Currently, there is no fully effective treatment for microgravity-induced bone loss, and counter measures against bone loss are a top space science priority."
For deeper reading try:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd
Re:1/r^2 kills this (Score:5, Informative)
The fact that the Sun's magnetic field is large isn't what protects us from cosmic rays. The Sun's magnetic field encourages particles to orbit the Sun. That doesn't help us. What helps is when a dipole field gets closer to you - like when the Sun sloughs off a bunch of plasma that drifts near you. Hence a Forbush decrease. What protects us on Earth is the Earth's magnetic field, and the atmosphere.
Anyway, it's relatively easy to craft magnetic fields to any shape you want. So high magnetic field on the outside, zero magnetic field on the inside. We're really good at that. And 5 tesla (50,000 gauss) should be about enough [thespacereview.com]. It has been studied.
The reason it's not ideal is because cosmic rays aren't all charged. Gamma rays make up a component of solar cosmic rays, and okay, there may (should) be a few neutrons from the Sun as well (though that part is really new and not well studied).
But magnetic shielding is very actively being looked at. It's just not an easy problem - we don't have very much experience with superconducting magnets in space, for instance.
Interestingly, one of the best things about this is that you don't really have to worry about the highest energy particles which will get through. Not only is the flux far, far lower, but they deposit less energy than lower energy particles which stop in your body. So it's pretty easy to figure out how high a magnetic field you need.
And smartass comment: magnetic fields don't drop like 1/r^2. Electric fields do. For a simple magnetic dipole, the field strength drops like 1/r^3. Different configurations drop differently, as well.
A solar physicist speaks... (Score:5, Informative)
The energetic protons are a real problem for man and machine. They arrive minutes to hours after the flare itself is seen. They have a high "quality factor", meaning they do a lot more biological damage than an equivalent ionizing dose of X-rays or gamma rays; and they tend to embed themselves in insulators, developing a humongous static charge that screws with electronic circuits and can burn out components. The clouds are more of a problem for planet-sized bodies (like the Earth) than for astronauts, but they do have some potential health consequences. They travel at "only" 1-4 million miles per hour, arriving at Earth about 1-4 days after the solar event.
Over the last three years we've had six or seven large flares that could have caused radiation sickness or death for Apollo astronauts (or Mars-bound astronauts with similar amounts of shielding to a mere Apollo capsule). That's enough that you'd have to expect at least one such event during a Hohmann transfer orbit to Mars, if you travelled at this phase of the solar cycle (declining).
The space station is largely shielded from the energetic protons, because it stays in low Earth orbit, underneath the Van Allen radiation belts -- Earth's magnetosphere diverts the protons away from the station. But the high energy galactic cosmic rays have no trouble passing through and hitting the station. So station astronauts are (probably somewhat) safer during solar maximum, but interplanetary astronauts are (probably) safer during solar minimum. Either way the radiation dose is a problem that has to be designed around.
Incidentally, the largest effect of solar activity on the space station is orbital decay! During solar maximum, the increased far-ultraviolet brightness of the Sun heats the outer layers of the atmosphere (the "thermosphere"), making them expand significantly -- that increases orbital drag a LOT. It's one reason (the other being delays in the Shuttle program) that Skylab re-entered the atmosphere before the Shuttle came on-line to provide additional boost. Skylab was launched during solar minimum in the mid 1970s, and the orbital decay projections were based on solar minimum conditions. It re-entered several years earlier than initially expected, because the atmosphere (and hence orbital drag) got larger in the solar maximum period of the late 1970s. The space station has similar orbital-decay issues; if you Google for the altitude-versus-time plots, you'll see that at its chosen altitude, the ISS needs to be boosted every six months or so, or it will spiral in and re-enter the atmosphere.
Re:hmmm, matter absorbing energy? (Score:2, Informative)
Looking on Google again I found what I'd been think of. It's the Geodynamo if anyone want to look for it.
"Currents flowing in giant loops through the earth's core."
You're pretty much correct there on how they think it happens.
Basically the guy noticed that the direction the molton core convects is different in some places than others. And it changes the way the magnetic flux acts.
When the convects in one direction, the flux goings in one direction; when it convects in the other the flux reverses the direction (which is what I was thinking of when I said about the North/South poles).
Lots of pretty pictures on a few sites talking about the Geodynamo, I'm sure there'd be more stuff around if anyone wants to look for it.
http://www.psc.edu/science/Glatzmaier/glatzmaier.
http://www.psc.edu/research/graphics/gallery/geod
The first two animations on that page show fairly when what's happening.
The core of the Earth is rather chaotic in terms of which direction the convection is happening in and therefore which direction the magnetic flux is in (this is what I'd been thinking of).
These bits change over time and move around to different points under the Earth's surface (think hotspots which move and cause chains of volanos which are all dormant apart from the ones at the end).
Which direction the flux moves in overall is essentially a complex summation of where these lines of flux are moving.
During the reversal lots of areas of convection change direction and change the direction of their flux. As they do so the overall lines of flux move and weaken, until they swap around.
This is quite an informative page on magnetic field reversals, and it talks about the Geodynamo at the end.
http://www.geomag.bgs.ac.uk/reversals.html [bgs.ac.uk]
Obligatory Wikipedia links:
http://en.wikipedia.org/wiki/Magnetic_polarity_re
http://en.wikipedia.org/wiki/Geomagnetic_reversal [wikipedia.org]
http://en.wikipedia.org/wiki/Geodynamo [wikipedia.org]
http://en.wikipedia.org/wiki/Dynamo_theory [wikipedia.org]
Speaking of astronauts..... (Score:3, Informative)
Some of the things they are talking about(from the official program):
The Genesis of Cooperation in Space: The Apollo-Soyuz Program
Tom Stafford
Panel Discussion (ASE Founders)
Loren Acton, Bertalan Farkas, Georgi Ivanov, Alexei Leonov, Vladimir Lyakhov, Dorin Prunariu, Rusty Schweickart, Vitaly Sevastyonov
Technical Session: International Space Programs Review
Chairs: Chris Hadfield, Leroy Chiao
NASA Headquarters Update: The ISS Program and Future Issues
Bill Readdy, NASA
Life on Station
Leroy Chiao, NASA
Report on the Canadian Space Program
Chris Hadfield, CSA
Report on the Russian Space Program
Yuri Usachev, RSC Energia
Technical Session: Crew Safety & Technical Issues
Chairs: Sergei Avdeev, Charlie Precourt
Shuttle Derived Vehicles
Mike Conn, ATK Thiokol
Maintaining On-Orbit Crew Proficiency
Chris Hadfield, CSA
Electromagnetic Radiation and Crew Health
Alexander Serebrov
Technical Session: Future Programs
Chairs: Michel Tognini, Yuri Usachev
Beyond the Moon: The Asteroid Option
Tom Jones
Kliper
Yuri Usachev, RSC Energia
Russia's Future in Space
Georgi Grechko
The Aurora Program
Piero Messina, ESA
There's some pretty big names in there, also note that they are talking about astronaut safety with regard to electromagnetic radiation.
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